The first presidential bomb shelter was located in an old vault under the Treasury, connected to the White House via tunnel.

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

The walls of the iconic dome are hollow and have a secret stairway.

In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.