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

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

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

A derelict bit of transportation infrastructure hidden in the woods.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

A wondrous old library overlooking the nation's capital.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

This grand gothic brewery has been pumping out suds for over a hundred years.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

This abandoned asylum was once a state of the art facility before devolving into one of the most deadly mental institutions in American history.

Ship skeletons haunt Baltimore's waterways.

One of the oldest anatomical theaters in the U.S. still in use was once the site of an infamous cadaver riot.

The haunting "Hell House Altar" is one of the few remnants of an abandoned college that has been a magnet for local legends.

A blank headstone topped with a pile of pennies marks the final resting place of the infamous assassin.

The site where Poe "in great distress, and ... in need of immediate assistance" likely died.

A museum dedicated to exhibiting remarkable outsider art.

It's not hard to see why the historic Peabody Conservatory of Music's library has been described as a "cathedral of books."

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

The California capital city once stood 10 feet lower than it does today.

Staircase winds down the side of Telegraph Hill through gardens, wild parrots flying overhead.