There's so much to do in Washington D.C. If you're planning on extending your trip, here are some ideas of things to do:
1) Visit the free monuments and museums at the National Mall. More HERE
2) Cruise around the Tidal Basin by pedal boat. More HERE
3) Visit the Spy Museum. More HERE
4) Tour DC landmarks on the Hop-On Hop-Off buss. More HERE
5) Visit DC Monuments by Night. More HERE
6) Visit the National Arboretum: https://www.usna.usda.gov/
7) Visit Arlington Cemetery. More HERE
HERE is the website for the Metro, DC’s subway system.