James Turrell's total color immersion art installation, hidden on the top floor of a luxury handbag shop.

It was once the base for a series of domestic terror attacks.

Atop this media building, two hives containing more than 30,000 bees keep the surrounding area vibrant.

A surprising, but overlooked example of geology in the middle of the nation’s capital.

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

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

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

This restaurant has been a haven for D.C.'s LGBTQ community since the 1950s.

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

The fountains of the U.S. Navy Memorial are annually salted with water from the Seven Seas as part of a nautical ritual.

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

Seemingly unremarkable items like empty sushi trays, chef hats, and freshness stickers are being preserved so future generations can look back on this beloved cultural import.

Largest Roman Catholic church in North America.

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

The national park was once a plantation estate.

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

People escaping slavery may have hidden inside a corpse vault.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

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

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

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

An artist's cute bronze subway sculptures belie his violent artistic past.

The ruins of an ancient Roman tomb hidden in the basement of a trendy clothing store.

Go inside to really appreciate this 500-year-old technological masterpiece.