America's Greenest Cities
No. 14 Washington, D.C.
Cynics may say that the city’s hot air counts as a sustainable fuel. But our nation’s capital made the top 20 most likely for its stellar mass transit system as well as the walkable Mall. Sunday is the best day to make the most of nine-mile-long Rock Creek Park, when the main arteries are closed off to cars for the sake of cyclists and pedestrians. On other days, you can always go hug a tree at the U.S. National Arboretum.