Free things to do:

Museum: Natural History Museum

The museum's 8-ton, 14-foot-tall African elephant is in a setting that re-creates the Angolan bush. The diorama also introduces important ideas in botany, entomology, mineral sciences, and zoology, as well as information on the ancestors of modern-day elephants and the elephants' importance in African cultures.
http://www.mnh.si.edu/ 

Just 3 blocks from Hotel Harrington, book your stay today at http://www.hotel-harrington.com