Abandoned to rust, decay, and creeping vegetation, monuments from before the Great War still stand amidst the ruins of Downtown DC: the Capitol, the Jefferson Memorial and the battered remains of the Washington Monument; this desolate area is known as Capital Wasteland. The central hub of civilization in the ruins of the former capital is Rivet City, based in and around the remains of an aircraft carrier carried far inland and beached by a catastrophic tsunami whose waters have long since receded. Other settlements include the towns of Megaton, Arefu, Tenpenny Tower and Paradise Falls. Movement between towns is done on foot through the wastes. In the Metro area, through surface streets, and where rubble blocks the streets, you can use the Washington Metro tunnels.
The Brotherhood of Steel community is stationed in the Citadel built in the ruins of the pre-War Pentagon. It is super mutants, who since emerging from their refuges have waged an unceasing war against humans to invade their territory, and the Enclave - the self-styled inheritors of the power of the United States government - under the leadership of their new President John Henry Eden, who are the biggest foes in the Campaign.