Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

100 years later, they're still down there.

Before Nixon, "watergate" meant canals.

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

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

Decades before the scandal, this staircase on the river was a literal "water gate."

Where the U.S. government kept its actual treasure, before Fort Knox.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

The "lovely red Vega" of the legendary record-settling pilot.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

A computer bug so primitive it was an actual insect.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

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

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

A nostalgic bibliographic gem.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

A painfully obvious spy house sits right across the street from the Russian Embassy.

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

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

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