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

A wondrous old library overlooking the nation's capital.

A historic ruin just 20 feet away from a busy highway onramp.

An unassuming, powerful monument north of the U.S. Capitol bears witness to the resilience of Japanese Americans during a time of grave injustice.

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

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

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.

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

Helen Keller once broke ground on this historic center for the study of technologies to benefit the hearing impaired.

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

The span is crooked and made from two older recycled bridges.

A Spiritualist house of worship where believers communicate with the dead in the spirit world.

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

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

This grand gothic brewery has been pumping out suds for over a hundred years.

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

People escaping slavery may have hidden inside a corpse vault.

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

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

Bar full of oddities, specimens, artifacts and homages to the great dime museums of the past.

Obscure Freemasons still live in D.C.’s largest private residence.

The first memorial dedicated solely to the Black troops who fought for the Union.

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.