There are two Circulator bus loops. One circles between the Washington Convention Center and the Southwest Waterfront. Along the way, it makes stops near the National Mall. The other bus travels between Union Station and Georgetown, with stops along K Street downtown.
The Circulator runs between 7 a.m. and 9 p.m., and it makes stops every 5-10 minutes. The bus fare (exact change) is $1.
More information about the bus as well as maps can be found on the Circulator website or at 202-962-1423.