Museum free. Live Butterfly Pavilion $6; $5.50 (ages 60+); $5 (ages 2-12); free to all Tues. (timed-entry ticket required).
Station: Federal Triangle
Daily 10-5:30. Extended spring, summer and federal holiday hours are determined annually. Live Butterfly Pavilion daily 10-5:15; timed entries are at 15-minute intervals and the wait can be up to an hour. Closed Christmas. Allow 2 hours minimum.