MR. KOJO NNAMDIFrom WAMU 88.5 at American University in Washington, welcome to "The Kojo Nnamdi Show," connecting your neighborhood with the world. When you stand underneath the National Cathedral, it's easy to be so struck by architecture, the soaring stone towers, the quirky gargoyles and the massive stained-glass windows that you overlook the postcard-perfect trees and the winding footpaths that surround it.

MR. KOJO NNAMDIBut such is the life of a landscape architect in the nation's capital whose works often get the least of our attention, even though the details of their designs are all around us: the benches where we rest, the paths we walk on and the flowers we smell. Together, they shape how we experience D.C.'s treasured public spaces and monuments.

MR. KOJO NNAMDIJoining us to explore the process of designing the unseen and often overlooked in D.C.'s urban landscape is Roger Lewis, architect and the "Shaping the City" columnist for The Washington Post. Roger is also professor emeritus of architecture at the University of Maryland, College Park. Roger, always great to see you.

MR. ROGER LEWISNice to be here again. Thank you.

NNAMDIAlso in studio with us is Michael Vergason. He is a landscape architect and the founder and principal of Michael Vergason Landscape Architects, LTD, in Alexandria, Va. Michael Vergason, thank you for joining us.

MR. MICHAEL VERGASONIt's my pleasure to be here.

NNAMDIIf you'd like to join this conversation, exactly how much do you know about what a landscape architect does, 800-433-8850 is the number to call. You can send email to kojo@wamu.org, send us a tweet, @kojoshow, or go to our website, kojoshow.org, ask a question, make a comment there. Do you pay closer attention to the architecture or the landscapes surrounding the architecture? 800-433-8850.

NNAMDIRoger, you say people who think of landscape architects as just glorified gardeners should better think again. Can you explain what sets the landscape architect apart from other architects and civil engineers and city planners?

LEWISWell, we can spend an hour on that. Well, I...

NNAMDIWe will.

LEWISI think the -- of course, architects primarily focus on the construction of buildings, designing things that -- the vertical construction, as we call it sometimes, that reside in, occupy landscapes. But the landscape architect generally is concerned with what happens in that realm that we -- most of us occupy using our feet, as well as our eyes, you know, the shaping, if you will, of the earth's surface. And that obviously is a broad -- I mean, that can be everything from someone's intimate garden to some -- a whole part of a city or a campus of a university.

LEWISIt's a very broad field. It used to be people thought landscape architects just came in and put some shrubs and trees around. And landscape architects today deal with the landscape at all scales, from very intimate to very, very monumental or very, very broad in (unintelligible).

NNAMDIWhat are the basic considerations that landscape architects will keep in mind when designing a space?

LEWISThat's a long list also. We should probably let Michael say something about that. I mean, it's a very large number of factors. Let's start with, you know, the local climate and ecosystem, soil conditions, functional agenda. I mean, it's a long list, just as it is for architects when they're designing buildings.

NNAMDIWell, I just got the list from the article you did in The Washington Post in 2006: topography, soil, hydrologic and geologic conditions, climate and microclimate, indigenous vegetation, wildlife habits, existing built contexts and existing regulatory contexts. Michael, maybe you can help to explain some of those for us.

VERGASONWell, I think it's a good list of individual pieces. I think the broader ideas that we deal with both cultural and natural systems and how those interact and relate to one another and the kind of purpose of making places for people that are healthy and uplifting and that have a strong sense of connection to their contexts so that the work we do, I think, at its best uses the existing conditions of the site, both natural and built, as a springboard for where it goes in terms of refining, improving those systems.

NNAMDIA lot of people worldwide will recognize many of this city's major landmarks, but the city's landscapes are less well-known even to residents of D.C., which might be why the American Society of Landscape Architects recently put together a guide to D.C.'s landscape architecture. You contributed several entries to the online guide, Michael. How do you think it might change how tourists and D.C. residents explore D.C.?

VERGASONWell, I do think it is -- and maybe I should not say it -- but surprisingly effective when the idea was first extended to me, and it all happened quite quickly. I didn't imagine it being as successful, as easy to navigate as good and consistent a review of sites in Washington. It's the product of the ASLA, which is a professional society of landscape architects.

VERGASONThey did an extraordinarily good job of managing a piece that used a great deal of voluntary time from individuals who provided critiques for a wide variety of sites across Washington, but they put them into a surprisingly coherent and navigable site that, I think, is a great asset.

VERGASONAnd I think people will use it, particularly with its application to iPhones, that will help move them through the city and encourage them to see places not just on the Mall but places outside the Mall that will spread that interest and appreciation of the richness of the city where landscape, I think, is such an important piece (unintelligible).

NNAMDIGlad you brought that up because the guide does cover a lot of spaces that are already marked on tourist maps, like the World War II Memorial, the National Cathedral. How do you steer visitors' attention from the landmarks to the landscapes that are framing those landmarks?

VERGASONWell, I think it goes back to the original question at the outset of your discussion and Roger's. And I'm not sure how much I think it ought to be steering specifically towards those landscapes but appreciating the fact that both are integrally related to one another. That is, the buildings, the city structure, the monuments of Washington wouldn't be what they are if it weren't for the landscape, that the landscape is an integral part of that place. You mentioned the cathedral at the outset and the soaring shrine that it represents.

NNAMDIMm hmm.

VERGASONBut that was carefully located. The site for it was carefully located on a high point of the city that overlooks the monumental core of Washington. And then the 57 acres that surround it, which is called the Close, is such an important part of the way you experience that cathedral that I'd never really want to isolate the attention on one or the other but bring the attention to the fact that the setting of these memorials and really the structure, the basic framework of the city of Washington, is really provided by its landscape and open space.

NNAMDIRoger, Washington's landmarks in the downtown core have millions of visitors every year where the landscapes surrounding these monuments. Were they designed to welcome a high number of tourists, and is there a broad philosophy in how these landscapes are created?

LEWISWell, there's no question that they were designed -- of course, in the beginning if you go back to the L'Enfant plan and subsequently the McMillan plan 100 years later, there was no question they were designed by thinking big, thinking about a lot of people and thinking about enabling people, visitors and residents to see things across great vistas, great distances at times.

LEWISAnd other times in those plans, we also know there are some spaces that are meant to be more urban parks -- or I should say parks that are framed by buildings and that are not necessarily two miles long. The Mall, Michael and I were looking at this before the show and confirming that, from the Capitol building to the Lincoln Memorial, it's two miles. And I think the city is a city that is very accommodating of large numbers of people.

LEWISI can't say the same thing about tourist buses, by the way. We'll come back to that. But I do think -- I think people see the landscapes. I think one of the points of the ASLA guide is to raise consciousness, picking up on Michael's point, of how much the landscape and the architecture are really of one -- a unity, something that is -- it really goes together.

LEWISIf you were to pick up the Lincoln Memorial and stick it on -- in the middle of the one of these one-block parks, it wouldn't be the same as it is, or the Washington Monument, the fact that this is this tremendously high vertical obelisk surrounded by this great expanse of open space, that's a composition that you have to take the landscape and the object together. They are not separable.

NNAMDIWell, just one indication of how effective the landscapes are, when you just said from the Capitol building to the Lincoln Memorial is two miles, it never occurred to me that it was that long, as two miles, because the landscapes occupy so much of my attention I thought it was maybe, oh, three quarters of a mile, something like that. On to Susanna in Fairfax, Va. Susanna, you're on the air. Go ahead, please.

SUSANNAHi, Kojo. How you doing? I listen to your program all the time. I would like to say thank you for all your guests. I'm currently living in Fairfax. I'm originally from Bologna, Italy. And I just want to say tomorrow is my Washington day for the simple reason that I need to go there and walk and admire. You were mentioning the cathedral. It's my perfect Zen place because it's a combination of harmonious, symbiotic relationship of a masterpiece of architecture and a beautiful garden all around.

SUSANNAAnd I want to thank you, all your guests, for the work they're doing because it's fabulous. The other place that I adore is Dumbarton Oaks, which I try to treat myself at least twice a year, in the fall and in the spring. And the other work that I admire very much is the new promenade. There was beyond the Capitol years ago, by the Potomac, you know, the walking promenade?

NNAMDIMm hmm. Yep.

SUSANNAYeah, which is absolutely beautiful.

NNAMDIThank you very much for that call. Michael, you talk about how the landscapes and the gardens of the National Cathedral offer a respite, if you will, from the city, something that I also have never thought of before, but instantly feel the minute I head on to those grounds.

VERGASONWell, Susanne, I liked your comments, and I think it's particularly interesting. I mean, Bologna is an extraordinary piece of urban, civic art, and in many ways, the exact opposite of Washington, D.C. Washington, D.C. is, as Kojo was just saying, really is defined by the vastness of its open space, which has both positive things, wonderful things as the degree that it can accommodate visitation, but then it has some things that aren't as good that Bologna does so beautifully, and that is tight urban streets and spaces and squares.

VERGASONBut the fact that you get out and see and appreciate those things that Washington has to offer in stark contrast to Bologna, I think, is quite beautiful. The National Cathedral does do that. It offers an extraordinary, I think, ensemble of small garden spaces that offer a respite from the city and kind of contribute to the spiritual quality of the place and its origin and were very much part of the original conception of the cathedral.

VERGASONOlmsted Jr. developed the master plan for the cathedral in 1927 and did a very, very thorough job not only of citing the cathedral but thinking about the way people approached it and how the landscape of the cathedral supported the basic mission of the place.

NNAMDISusanna, thank you very much for your call. I'd like to go to Denise in Alexandria, Va., next. Denise, it's your turn. Go ahead, please.

DENISEWell, I just want to say that I decided to move to D.C. after I rented a bicycle and fell in love with the city. So that was one thing.

NNAMDIYou see the city in much the same way that Roger Lewis sees the city but go -- on his bicycle. But go ahead, please.

DENISEAnd my question is, how is the field changing considering global climate change, rising sea levels and restoring the landscape after these huge storms that are becoming more frequent?

NNAMDIAnd I suspect that's for both architecture and landscape architecture. Roger.

LEWISWell, my last column in The Post was about that. I mean, the first thing is we probably shouldn't be building on some of the landscapes we've built on. I think one of the lessons of Sandy was that there are, you know, building -- taking 2-by-4s and putting up wood-framed houses on barrier islands or behind primary dunes is not a good idea. And so...

NNAMDIThe New York Times reports today that the flood insurance for places like that will be going up precipitously.

LEWISWell, they probably shouldn't even provide it. The price shouldn't be insurance. But in any event, you know, the issue -- dealing with a landscape in part is about preservation and conservation. There are places where you shouldn't build. There are places that are intrinsically suitable for building and where building makes sense. So certainly one of the first things we ought to try reach consensus on in this country, in this culture, is that they're recognizing that there are places we probably shouldn't build.

LEWISI -- The Post took out one line in my article. I mentioned that if we were starting today trying to build Las Vegas where we don't have water in great supply, you probably wouldn't get a permit to build it, like, you know, the same would be true of New Orleans. And we look at Amsterdam, and we think, well, there are way -- we can engine our way through this. But, in fact, I would -- I don't know whether Michael agrees with this, but I would think that most landscape architects would say that, you know, building next to the sea, below sea level is probably not a good idea.

VERGASONWell, I think all landscape architects would say that, and, you know, I think that what's happened of recent is that there's a broader understanding of what I think landscape architects have been espousing for some time, that there needs to be a clear logic in thinking about the way we occupy the land that's built on an understanding of the natural systems that define it. And that we build in a way that allows us to maintain and ideally even improve the health of those natural systems rather than building in ways that, in fact, work in opposition to them.

NNAMDIGot to take a short break. Thank you very much for your call, Denise. You, too, can call us at 800-433-8850. What are your favorite public spaces in and around D.C., and how do landscapes contribute to your enjoyment of those spaces? 800-433-8850. Send us a tweet, @kojoshow, or email to kojo@wamu.org. I'm Kojo Nnamdi.

NNAMDIWelcome back. We're talking about landscape architecture in general and Washington, D.C.'s landscape architecture in particular with Roger Lewis, architect and the "Shaping the City" columnist for The Washington Post, also professor emeritus of architecture at the University of Maryland, College Park, and Michael Vergason, landscape architect and the founder and principal of Michael Vergason Landscape Architects in Alexandria, Va. Taking your calls at 800-433-8850.

NNAMDIWe got an email from Lorraine in Reston, who says, "How much freedom does someone like Michael feel to built landscapes that don't exist naturally: ponds, lakes, hillsides? If it looks great, I probably won't care if it's something created by God or something engineered by a clever group of landscape architects." Michael?

VERGASONWell, I feel very optimistic and don't hesitate whatsoever to create landscapes. Most of the landscapes we deal with today are, in fact, created -- affected to a degree -- to a large degree in one way or another that they really are not natural landscapes anymore. They may carry the kind of working systems of a natural landscape, and I think that's what we need to try to do in the work we do.

VERGASONBut not necessarily by mimicking or pretending that we're doing anything other than creating landscapes that work through natural systems as opposed to necessarily appear to be natural or hesitate to create landscapes that do appear natural.

NNAMDIThe landscape architect has to work within spaces defined around architecture as well as space confined by the surrounding urban centers. How do you approach that kind of challenge going into a project?

VERGASONRestate that question for me, Kojo.

NNAMDIWell, you're working within spaces that are defined by the buildings in it, but you're also working in spaces that are confined by, oh, if you go to, I guess, a L'Enfant Plaza, and you're working within a space that's kind of surrounded by all kinds of buildings. What was the challenge there?

VERGASONWell, the challenge is to understand the framework that existing buildings establish for a place, what opportunities they represent and what restrictions they represent. It not an unusual position to be in. In a lot of cases, we're working within well-established frameworks, and it's at a position that I enjoy.

VERGASONIt is one which is actually generally true, I say, of almost everything we do and that is that it never starts with a blank canvas, whether it's the built framework architectural or otherwise, city structure that establishes the framework within which we work, or it's a natural system of framework. What we rarely do is really start with a blank canvas. So I enjoy.

VERGASONAnd my background is in architecture as well as landscape architecture, so I come to it with a love for both and with really an interest in developing places that have a clear, coherent feel where the landscape and the architecture are in dialogue and co-exist as beautiful companions. I would use it to say too that I think the best work that we do in our profession is truly collaborative, and it's a position of design, an approached design which we enjoy very much.

VERGASONAnd I think the McMillan plan, which is an adaptation or refinement of the L'Enfant plan done in the early part of the 1900s, is a beautiful example of collaborative design between architects, landscape architects, artists and engineers where all are at the table discussing issues simultaneously and really developing a vision for a place that looks at all of those issues simultaneously in the appropriate balance.

NNAMDIGlad you mentioned Pierre L'Enfant because, Roger, D.C.'s design owe some credit to landscape architect Frederick Law Olmsted Jr., who Michael mentioned earlier, and architect Pierre L'Enfant. Do their visions of the city still influence its design today?

LEWISOh, I think so. I mean, I think so. The -- one of the things -- one of the points I hope that's coming through is that there's some ideas and principles that are timeless, that are not just matters of fashion or style. And, for example, we know right now there's a current debate going on over a space of the sort you described. That is, a frame figural space framed by architecture, Eisenhower Memorial...

NNAMDICorrect.

LEWIS...which we've talked about several times, this 4-acre site that I think is, in fact, a good example of what Michael was talking about, a place where there is an existing context, an existing framework, existing conditions. And as everybody who I think has heard us talk about this knows, I think they kind of did it backwards. I think what they should have done is hired a team headed by a landscape architect to design an urban space in which Mr. Gary or whoever could design introduce some kind of memorial.

LEWISThey didn't do that. I think we should point that they are going at it, in my opinion, slightly backwards. I -- But I think the -- again, what -- just to echo what Michael had said, that there's -- there are ideas that are timeless that we -- there are things that I think were done by Olmsted for that matter. I think there are things, you can go back centuries, ideas that we still respect and admire and can adapt for today's conditions.

NNAMDIOn to the telephones again. Here is Dave in Alexandria, Va. Dave, you're on the air. Go ahead, please.

DAVEThank you for taking my call, Kojo, and thank you to your guests. I have a question about the layout of Washington, D.C. I've heard over the years that the circle in the city planning were designed as a defensive measure that you could take six cannons and maybe 50 men. And by pointing the cannons down all those roads, you'd be able to control significant parts of the city, that that was done by design. My question is, is that true, or do we know that's true? And also, if it is true, was that contemporary? Was that a typical thing for cities at that time?

NNAMDIWell, Dave, it's funny that you raised that issue in terms of why they were designed because I had a question of a different nature about the same phenomenon, and that is, the diagonal streets in D.C.'s downtown grid intersect to create these pockets of architectural spaces like the circles, like Dupont Circle. And I was going to ask both Michael and Roger about the design of those small urban parks. But, first, you might want to talk first, you, Roger, and then Michael about why the city was designed in that way.

LEWISWell, that's a...

LEWIS...that's another similar topic. I mean, we can talk for a long time about the L'Enfant plan. I think there has -- I've heard the story -- speculation about defensibility being used by L'Enfant. He was, after all, a military engineer. But I think it was probably not the primary consideration. I mean, I think from what I have learned over the years, my -- I'm going to look -- hope to hear what Michael wants to say about it.

LEWISBut I think they were -- I think what L'Enfant did was he looked at this landscape, this existing landscape with the rivers and the topography and the notion, if you will, the kind of symbolic opportunity of creating points on this landscape where the legislator could set an executive -- could set -- and I think the notion of superimposing a rectangular grid with a diagonal grid which he had knowledge of from what was happening in places in Europe such as Versailles, I mean, I think -- I don't think he was thinking about 90 men and canons and the circles necessarily. But...

NNAMDIMichael, what do you think?

VERGASONI think the same. The origins of the straight avenue did grow from the idea of defensibility, but it developed into a kind of stylistics, baroque signature in urban design. And I think L'Enfant's application here was more in that latter than in the former. And I do agree with Roger. I think the plan for Washington is one of the great urban plans of the world, a beautiful, beautiful overlay of Jefferson's idea about a simple, gridded, plaid network of streets that represents the Democratic idea of uniform -- uniformity, of everything being equal overlaying with this beautiful radiating system of avenues.

VERGASONBut the real genius, I think, of L'Enfant's plan is, as Roger was intimating, was the way that he adapted it to the topography and the natural systems of Washington. Not only the river basin and its lowlands, but he picked the two high spots within reach of one another to put the president's home and Congress and then connected those with one principle avenue, that, of course, being Pennsylvania avenue.

VERGASONBut then out of each one of those, there's the spokes of avenue six that lead into the White House and eight that lead into the U.S. Capitol that focused all the attention on those pieces, on those high spots, using grand spaces, which was very much a part of the dimension of baroque planning. But in this case, I think, the beautiful thing, he used -- and it's not just the parks and the reserves and the squares but the streets and the avenues that are an important part of the framework of that plan.

VERGASONAnd he used those to establish a presence across a big landscape that had, at that time, very, very few people or buildings in it. And, of course, the city has grown into that framework in quite a beautiful way. But it's a plan that's allowed the city to develop and evolve over a long period of time, I think, because it had inherent strength in it which, as Roger said, was based on principles and ideas as opposed to style.

NNAMDIDave, thank you very much for your call. We move now to Mike in Bowie, Md. Mike, your turn.

MIKEHey, Kojo. How are you doing?

NNAMDII'm doing well.

MIKEI can't let a discussion like this go without talking about the Tidal Basin. I just rediscovered that a couple of years ago on my way home from Virginia, and this is such a beautiful walk. You see every iconic building in D.C. I can't recommend it enough.

NNAMDIThe Tidal Basin. Mike, what do you enjoy most about the Tidal Basin? Is it the combination of monuments and landscape that you go for?

MIKEYeah. And then, you know, combined with the cherry blossoms and the spring, you know, it's just spectacular, you know? I mean, you walk around and, you know, from different vantage points, you can see the White House. You can -- you look down and you can look through the gap in the buildings and see the Capitol. You can see the tip top of the Washington -- of the Lincoln Memorial. It's just beautiful, you know, Jefferson Memorial, Martin Luther King, FDR.

NNAMDIRoger.

LEWISWell, Mike is making a point. Again, another important part of landscape architecture's mission is to think about movement through the physical environment, through landscapes. I mean, I think one of the things that Mike is pointing out is that these are not static in a sense that, I mean the trees and shrubs and everything else, they don't move. But you move.

LEWISAnd so I think one of the things that is really wonderful about good landscape design is that it both enables movement but also enriches the visual and spiritual experience of that movement through that environment. And I think Washington does -- has a lot of wonderful places where -- and I'm not talking about so much movement in automobiles. I'm talking about movement on foot, movement on bicycles. It's a great place to move.

NNAMDIAnd we'll get to bicycles in a second. But thank you for your call, Mike. We got this email from Dason -- from Jason. And, Michael, earlier you talked about architects and landscape architects and engineers and everyone else getting together.

NNAMDIJason writes, "I found that when working in public space, there are pressures to conform to the least controversial solution, a problem that must seriously inhibit the creativity of landscape architects. How much of the landscape architecture in evidence in D.C. is the result of the creative achievements of individuals and small groups, and how much of it is designed by committee? How would you suggest we alter the design process for public spaces to allow for the original vision of the creative forces to be in greater evidence?" Good question, I think.

VERGASONIt is a great question. As I said earlier, I think landscape architecture is very much a collaborative art. And it's a collaborative art in part because so much of what it does deals with the public realm. And I think in the end that the planning process and the public component of that planning process is an essential part of the success of any design. I think your statement at the outset there that the pressure to conform, in fact, perhaps leads us towards common denominators and easier solutions. But I know that that's not always the case.

VERGASONI think that there are an awful lot of good examples where the strength of an idea can carry it through what can otherwise be something less than what is conventional or normal. And I think there are good examples of that. And then there are probably as many good examples of the way that a public process has moderated an idea to bring it into a position, a balance that, in fact, may well represent better position to be than it might have originally been. I do think that landscape is a practice that depends less on authorship than some other arts, and in the end, that that's one of its positive aspects.

NNAMDIHere is Don in Hillsboro, Va. Don, your turn.

DONHi. I wanted to call in on the question of the military significance of the traffic circles and the alignment of the avenues. And this is something I spent some time trying to find out the source of, and it's an absolutely untrue theory. I -- it actually originated in the middle or later 19th century as an explanation after the fact based on parallels with the then design of Paris. But there was absolutely no consideration by L'Enfant of the military significance of the alignment of avenues or circles.

NNAMDIOK. Don, thank you very much for clarifying that issue. But it raises another issue, Roger, and that is, how do security concerns govern design choices in D.C. Center? The Landscape Architect's Guide describes the stretch of Pennsylvania Avenue right in front of the White House as an inviting and flexible space. Flexible I find to be an interesting word. How does that design balance aesthetics with security concerns?

LEWISWell, the -- I had a little bit of personal involvement in that issue. After the Oklahoma City bombing, I was asked to serve on a committee by GSA to look at the Federal Triangle. The Department of Justice, the people in that building were terrified. They were afraid they were going to -- a truck full of explosives was going to come over the curb and barrel its way into the -- through the facade of the Justice Department.

LEWISAnd we talked. This committee convened, and we -- they were prepared. Justice Department wanted to put up barriers immediately, surround the place with Jersey barriers and everything they could do and think of to stop it. We -- after telling them, look, if you're going to stay in the city, you may have to take a little bit more risk than you would if you were living in -- if you were out in Reston or somewhere more distant, but we said, you know, this isn't -- this becomes an issue for streetscape design.

LEWISThis is -- this, again, is a landscape architecture challenge. How do you design a street? Streets are part of the landscape, of cities. They are landscapes. How can they be designed so that you, in fact, could stop a vehicle from coming across the sidewalk and barreling the building, yet not have it look like you're creating a fortress or creating tank traps or whatever?

LEWISAnd the good news is GSA listened, and others listened, and there have been some measures taken over the last 20 years to solve this problem in a way that's aesthetically appropriate without making everybody feel like they're walking through some kind of defense barrier.

NNAMDIEverybody except Tom Sherwood, that is. Michael Vergason, care to comment on that?

VERGASONWell, a couple of thoughts. One is that I think we are getting better. One is that I think that issue is here to stay. I don't think it's going to diminish a great deal or disappear. Absolutely, it will not disappear. I think we're getting better at it. I think the -- Olin's work on the Washington Monument is a beautiful, beautiful example of the way that those concerns can be addressed and result in a landscape that actually is extraordinarily beautiful.

VERGASONI think Rogers -- Roger Marvel's work, architectural firm from New York City, on Wall Street is a clear demonstration of the way those issues can be transformed. They, along with Quennell Rothschild, were selected recently to redesign South President's Park and the Ellipse to address just those issues, and I'm confident that they'll demonstrate the finesse that they apply to that issue. So I think we'll get better at addressing security concerns within the format of both functional and beautiful landscape.

NNAMDIDon, thank you very much for your call. Got to take another short break. When we come back, we'll continue this conversation on D.C.'s landscape architecture. If you have called, stay on the line. But the lines are all filled. So if you're still trying to get through, send us email to kojo@wamu.org, or send us a tweet @kojoshow. I'm Kojo Nnamdi.

NNAMDIWelcome back. We're talking about D.C.'s landscape architecture with Michael Vergason, a landscape architect and the founder and principal of Michael Vergason Landscape Architects in Alexandria, Va. And Roger Lewis is with us. He is an architect and the "Shaping the City" columnist for The Washington Post. He's also professor emeritus of architecture at the University of Maryland, College Park.

NNAMDIRoger, I'd like you to pick up where you left off during the break. You were talking about the Washington Monument and how it's sometimes difficult to even notice or observe the landscape there and how it influences the environment.

LEWISWell, I was just footnoting what Michael had said earlier, which is that design, that essentially manipulation of the topography, very subtle manipulation of the topography, of the use of low retaining walls and creating pathways, it's done in a way that, I would say, I would guess that 99 percent of the people who visit the Washington Monument are not aware that that landscape that's been shaped around the monument, in fact, is in part driven by security concerns. I would be very surprised if anyone realizes that it's been created, in part, to ensure that no vehicle can get close to the monument.

NNAMDIThis email we got from Jill in Georgetown: "Can we talk about the genius and beauty of Dumbarton Oaks some more? I live down the street and spend so much of my time there and in Montrose Park farther down on our street, two of the most underrated gems in the entire area. The cemetery there is also jaw-droppingly beautiful and moving." Well, you started it, Michael Vergason. Care to continue?

VERGASONWell, I was saying, actually, during one of the breaks after -- I think it was Suzanne that called early on, and we didn't get back to touching on her comment on Dumbarton Oaks.

VERGASONBut that, certainly from my opinion, Dumbarton Oaks is one of the great American residential designs in the country and such an extraordinary jewel, so wonderful that it's publicly accessible, such an extraordinary place to go to, I think, understand some of the origins, be it to experience work of American design and landscape architecture, but also just such an extraordinary respite, a wonderful place to be within the city, and, of course, as you say, attached to the cemetery and Dumbarton Park, quite a beautiful ensemble of places.

NNAMDIOne entry in the Landscape Guide is different from the others. It explores D.C.'s bicycle network. How does that fit into the definition of landscape architecture?

VERGASONWell, I, you know, I had said during one of the breaks as well, I thought it was important that we point out that the streets and the avenues are as much a part of the landscape of Washington and certainly the framework of L'Enfant's plan as the parks and squares that are more traditionally considered to be landscape. *One of the interesting things about Washington is the width of the avenues and the streets, and those were a result, in part, of the interest in expansive space as a kind of baroque idea about landscape.

VERGASONBut I've always understood, although I've never read a verification of this, that they were also a byproduct of the law that was established for the purchasing of land, which said that all land would be paid for, I assume, at a fair market price, with the exception of those lands that were devoted to public use and enjoyment.

VERGASONAnd that, of course, meant the reservations and the parks and the streets. So streets end up being unusually wide. And one of the benefit to that -- it has it's downside as well, but one of the benefits of that is that the streets have been able to be adapted to include bicycle routing.

VERGASONAnd I think one of the more phenomenal things that's happened in Washington over the last 10 years is the degree to which -- and I think there have been some 50 miles of bicycle delineations, bicycle routes of different sorts added to the streets of Washington. And I think it's transformative in its quality and character and the image it presents as a city but also in the way the city gets used.

NNAMDIIn 2000, Roger, the city had, oh, three miles of bicycle lanes. Now, 10 years later, the city has, oh, more than 50 miles of bicycle lanes, and we seem to have accomplished it without any major disruptions.

LEWISAnd more to come, more to come, and that's -- this network of bike share -- this bike sharing network is also expanding, has been a great success. It's -- I think the -- I think there are some places in the city where there are still a little bit of conflict from time to time, which we've read about in the paper. But yes, I think it's wonderful that they're finally committing to recognizing that bicycle travel is -- as a valid way to get around the city as moving in automobiles or on transit.

LEWISI mean, I think that we're heading toward a city. I think this is going to be really a wonderful city when you really have all of these modalities of travel to chose from -- walking, biking, transit, driving -- and that can only be for the better. I mean, in the long -- we -- right -- I consider right now as a bicyclist that we're still in the training stage. We are training the drivers of cars, those of us who riding bicycles and vice versa to co-exist on these wonderful landscape streets.

NNAMDIGot this email from Jared in Southwest Washington," I worked in Southwest beneath Independence Avenue. Quite simply, we need the help of Roger and Michael in that part of the city. Concrete, concrete and concrete. Our access to the water is blocked by the epic disgustingness of the expressway. I wish we could get a do-over to beautify that corner of the city and that we could do it fast, like in that old video game 'Sim City' where you can build your own city.

NNAMDIAs is, the built architecture is ugly, and I find it disrespects what could be a beautiful landscape from L'Enfant Plaza eastward." Care to comment, Michael?

VERGASONWell, there's a general recognition of just what you have said there about that portion of the city and a great deal of effort on the part of the National Capital Planning Commission, as well as the Commission of Fine Arts to jumpstart efforts in that direction. That is to humanize that portion of the city, to extend the qualities of the mall and the daily life of the city into that area that's dominated, not just by highways and freeways but federal occupation to bring it more into the daily life of the city and to make it more humanistic in its character and quality.

VERGASONI don't think that this is anything that's going to happen overnight, and I know it's not going to happen overnight. Evolution of a city is a slow process, very much a kind of temporal art or urban design as is landscape architecture. But there is recognition of just the issue you talked about and a great deal of attention and energy going into it right now.

NNAMDIThis is for you, Roger, an email from Tom. "When the old Washington Convention Center was raised, there was grand talk of this once-in-a-lifetime opportunity to build something great in the six-square block site in the heart Downtown. It looks like what we're getting is more look-alike, 12-story office buildings bunched together with no open space. Is this a missed monumental opportunity?" asks Tom.

LEWISI have to agree. I've watched this -- I've gone by there and watched this project developing. Also, I'm aware that they cut back substantially. There was to be a large -- fairly large public civic space which got shrunk. Yeah, I found it underwhelming. I'm -- I've been little bit disappointed in the architecture. They went out and hired some well-known architects. I think we're not getting necessarily the architecture of the quality I'd hoped for. No, I -- I'd -- I mean, I should suspend judgment a bit. It's not done.

LEWISI'm sure they'll plant a lot of trees along the streets -- along in the streets inside the -- of the interior. I mean, it'll be probably not dreadful. I don't think it's going to be dreadful. But it's not -- in my opinion, not what it could have been. I think -- I do want to suspend judgment until it's all done.

NNAMDIUntil it's all done. Here is Peter in Washington, D.C. Peter, you're on the air. Go ahead, please.

PETERYes. I have a question for Michael Vergason -- I'm a colleague. He'll recognize me -- more in terms of general theory in a way people can understand landscape architects. I've always considered landscape architecture to be no different from architecture, same issues, simply different materials. I wondered if he'd like to comment.

NNAMDIMichael.

VERGASONYes. Hi, Peter. You know, I think landscape architecture defies simple definition. We started out with that in a way. I've never heard a good, clear, simple definition of the profession that's both coherent and concise. But I do think, you know, one way you could see it is that we do with the land what architects do with buildings with a few, I think, very important distinctions. Buildings have definitive perimeters. I think the landscape is open-ended. It is the kind of extended matrix so that everything we do has a context to it.

VERGASONThe second is that buildings are, by comparison, at least static and the landscape is -- and I think mentioned it earlier -- by its basic definition, ever changing. So it's a very temporal art. And the third is that it's a very much more collaborative piece because it deals with the public realm. So I think that comparison architecture is good with a few important distinctions.

NNAMDIPeter, thank you for your call. Here is Lucy in Washington, D.C. Lucy, your turn.

LUCYThanks very much for taking my call. I really enjoyed the -- this discussion. You had asked earlier about one favorite spaces in Washington. And one of my favorite spaces has always been the Smithsonian Gardens. And I'd like to recommend to your listeners a really good book that was -- it's called "A Guide to Smithsonian Gardens" by Carole Ottesen.

LUCYIt has lots of really good -- it has wonderful photographs and lots of really good information, both for the cultural and historical, that shows how the Gardens had evolved over the years. But in addition to that, I recently come across a book by the same author, Carole Ottesen, that is called "Dying for the Christmas Rose." And in this book, Carole, as a grandma, has turned from horticulture to crime. It's a wonderful, who-done-it murder...

NNAMDIOK. That's a severe turn you took for us there, Lucy. But thank you very much for your call. One more quick endorsement of Smithsonian Gardens, and that's from Tanya. And, Tanya, you have about 30 seconds.

TANYAHi. I just wanted to say the area around the Castle. It's one of my favorite places in Washington. It's just -- it's such a sense of beauty. It fits with the building really well, and yet you can find little secluded spots to sit and feel like you're by yourself.

NNAMDINow, do you spent more time inside the Castle or outside?

TANYAI spend more time outside.

NNAMDIOK. I thought as much. Thank you very much for your call, Tanya. And I'm afraid that's going to have to be it. Michael Vergason, thank you so much for joining us.

VERGASONThank you. My pleasure.

NNAMDIMichael Vergason is a landscape artist, and the founder and principal of Michael Vergason Landscape Architects in Alexandria, Va. Roger, always a pleasure.

LEWISLikewise. Thank you.

NNAMDIRoger Lewis is an architect and the "Shaping the City" columnist for The Washington Post. He's also professor emeritus of architecture at the University of Maryland, College Park. And thank you all for listening. I'm Kojo Nnamdi.