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

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

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

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

A super-sized promotional trick that is now a D.C. landmark.

The national park was once a plantation estate.

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

There’s a hidden military meme engraved on the World War II Memorial.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

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

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

A nostalgic bibliographic gem.

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

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

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

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

Home to items never before seen by the public.

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

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

The United States Capitol's former columns still stand.