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

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

The famous abolitionist’s preserved estate is one of Washington's finest monuments to its great Black citizens.

The national park was once a plantation estate.

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

A rotating cast of guys and dolls in front of a Washington, D.C. building.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

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

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

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.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

A historic neighborhood church is reborn as a psychedelic arts collective.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Home to items never before seen by the public.

The site of the climactic scene from the classic horror film is now a historic landmark.