The oldest continuously operating fish market in the United States.

The national park was once a plantation estate.

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

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

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

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

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

A derelict bit of transportation infrastructure hidden in the woods.

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.

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

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.

The United States Capitol's former columns still stand.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

The vast, legendary catacombs hold secrets much stranger than stacked bones.