Lansdowne Resort? It's not actually a city, which is why it wouldn't appear as one.
http://www.lansdowneresort.com/It's right outside of Leesburg, which is a little more (I think) than 15 minutes from Dulles. Leesburg takes me the better part of an hour to get to on the rare occasions I play paintball out there.
By that time, I'll have moved out of Northern VA, so I won't get to say hi. But if you can do it, definitely take some time to tour the Udvar-Hazy annex of the Air & Space Museum, just south of the Dulles Airport perimeter fence. There's also a Ferrari/Maserati dealership between the airport and Leesburg/Lansdowne that is interesting.
