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.

This tiered waterfall is so pretty it may cause visitors to cry tears of their own.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

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

Ruins of the elaborate house where the enigmatic costume designer threw glamorous parties for New York's theatrical elite.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

The bank that helped fund the Mexican-American War and the purchase of Alaska met its downfall after helping Augusto Pinochet launder money.

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

An overlooked memorial honoring the local Washington residents who died in World War I.

‘Bush the old fire dog died of poison July 5th, 1869. RIP.’

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

The national park was once a plantation estate.

A portal into the bricked up canal that runs through the heart of Washington D.C.

People escaping slavery may have hidden inside a corpse vault.

An obscure federal monument honors the French diplomat who served as Ambassador to the U.S. during WWI.

The school tested mustard gas for the U.S. Army during World War I.

Every drop of D.C. tap water flows through this old waterworks.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

The oldest continuously operating fish market in the United States.

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