Washington's iconic carousel has a nice piece of Civil Rights history.

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

People escaping slavery may have hidden inside a corpse vault.

The United States Capitol's former columns still stand.

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

There's an old indoor swimming pool hidden directly underneath the White House Press Briefing Room.

Home to a vast and influential collection of Shakespeareana.

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

An easily overlooked memorial to a Ukrainian famine-genocide that killed over 4 million people.

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

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

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

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

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

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

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

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

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

A stark reminder of the huge nuclear weapons plant that once stood on the site and its effect on the surrounding area.

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

This naturally-sourced hot spring is now home to a clothing-optional resort.