Massive Washington Dulles International Airport is 26 miles west of DC.
From DC, use the Arlington Cemetery (Blue Line) to get to the cemetery and the Pentagon (Blue and Yellow Lines) stations to visit Pentagon sites. Ride the King St-Old Town (Blue and Yellow Lines) station for most of Alexandria’s sights.
In Alexandria, a free trolley runs along King St between the Metro station and waterfront every 15 minutes from 10am to 10:15pm Sunday to Wednesday, and until midnight Thursday to Saturday.
Seasonal water taxis connect Alexandria with National Harbour, MD, and with Washington Harbour in DC. There are also seasonal boat trips to Mount Vernon from SW Waterfront in DC and from Alexandria.