America's first federal monument.

Built by the patriotic residents of Boonsboro in a single day.

A priceless collection of the Nation's cryptologic history.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

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

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

The national park was once a plantation estate.

This small city where almost everyone lives in the same building can only be reached via North America's longest tunnel.

A trading post in the North Pole where children send letters.

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

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

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

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

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

Decades before the scandal, this staircase on the river was a literal "water gate."

Rumor has it the hot dog stand was targeted by two Russian nuclear missiles.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

This lovely picnic spot featuring thunderous jet landings is an aircraft spotter’s dream.

The only place for a truly presidential dram.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

Site of a classic 19th-century physics experiment to prove the earth is rotating.

A majestic lion statue guards this Parisian botanical garden, and feeds on an unsettling item.