Politically one of if not THE most important city in the world, Washington is always well worth a visit. Whether you take a tour of the dignified White House, climb up Capitol Hill or wander around in beautiful, historical Georgetown the city is certain to impress. 

An excellent free audio guide for Washington could be found on the website of Ten Toe Tours, but unfortunately the service has been discontinued. There is no iAudioguide for Washington yet, so please be patient until the iaudioguide is released.