The White House is the closest D.C. staple being only 1.5 blocks away from the St. Regis hotel. Information for booking tours can be found here: https://www.whitehouse.gov/visit/.
Head to the Old Post Office Pavilion tower for one of the best views in the city.
You can see a play at Ford's Theatre or tour its historic grounds.
Across the street from our first apartment in D.C. towers the Washington National Cathedral. Visit the Bishop's Garden on its grounds or the adjacent cafe Open City for a coffee.
McPherson Square is a metro stop on the orange, blue, and silver lines. These lines will take you down closer to the National Mall, or within a 15 minute walk to the shops on M Street in Georgetown.
Farragut North is a metro stop on the red line. The red line will take you north into Dupont Circle or east to the grand Union Station.