Williams is a historic preservation expert who lives in the District and recently published his 15th book, "Lost Washington, D.C." A "house historian" and consultant, Williams has also written several walking tour books, including "The Historic Homes of JFK" and "A Walk Through Central Georgetown." He is also the president of the Historic Congressional Cemetery on Capitol Hill.

What inspired you to write about the long gone buildings of D.C.?

I know there were some other similarly themed books out there, but I kind of wanted to bring in something new ... and also to kind of weave in stories about the buildings, not just feature a building and the one that was torn down. Like stories about the people that lived in it or designed it, or activities that happened there.

Any favorite stories?

Yes, when we found out about the Krazy Kat Klub [a 1920s Bohemian joint near Thomas Circle that featured a treehouse]. I can't imagine getting that through a liquor board today, serving liquor 20 feet up in a tree!

What's "lost" about this city?

I think what's really lost in D.C. now is there used to be a really residential living core downtown, and it was on the scale of a typical townhouse. Now, downtown D.C.'s grown so large that the people left down there are in large high-rises, and its really got a downtown feel. It's really evolved into that over 200 years.

What's your favorite building in D.C.?

There are two houses on the south side of Logan Circle ... they're now all condos. It's my favorite because I watched it when it was in a really dilapidated state and no one was able to live inside it. And to see it restored well, and now it's one of the nicest historic houses on Logan Circle -- it's just a nice story.