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

These abandoned waterworks are crumbling into the Potomac River.

Press 1 for knock-knock jokes.

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

100 years later, they're still down there.

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

Look closely and you’ll notice that the color changes a third of the way up the tower.

There’s a special club house at the top for the bell ringers.

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

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

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

Amid the sprawling Defense Intelligence Agency Headquarters is one of Washington's least accessible museums.

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.

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

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

Where the U.S. government kept its actual treasure, before Fort Knox.

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

The "lovely red Vega" of the legendary record-settling pilot.

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

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

For 60 years, the academy had no permanent location until members voted Washington D.C. as its forever home.

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

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.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.