World's first "penitentiary," meant to be humane, drove men insane.

Yo, Adrian!

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Berkeley Hot Springs presents to you "the only outdoor monument to presidential bathing."

Outsider art meets paleontology at this roadside reptile repository.

Captain John Smith thought these cliffs were amazing in 1608 but sharks thought so 20 million years before him.

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

A pre-Industrial Age iron furnace and the site of a nearly-forgotten piece of Black history.

The whole world in one water tank.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

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.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

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

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

The most accurate timepiece in the world.

A museum dedicated to exhibiting remarkable outsider art.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

A former major munitions plant that has been converted into a sprawling art space.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

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 United States Capitol's former columns still stand.