Rare recess caves fill this unbelievably beautiful Ohio park.

An immersive art experience built by local arts collaborative, Factory Obscura, in the building formerly known as The Womb, a psychedelic arts center founded by the frontman of the Flaming Lips.

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

An Industrial Revolution-era public work that purified water using nothing but sand.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

People escaping slavery may have hidden inside a corpse vault.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

A wondrous old library overlooking the nation's capital.

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

The site of the climactic scene from the classic horror film is now a historic landmark.

The United States Capitol's former columns still stand.

This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

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

A historic neighborhood church is reborn as a psychedelic arts collective.

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

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

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

This demolished goliath of American industry once loomed over the depressed town it once made thrive.

North America's oldest quarantine facility was built in response to Philadelphia's 1793 yellow fever outbreak.

A giant ball made from pieces of an old Jeep.

A hidden piece of Altoona's railroad history in a long-forgotten abandoned town.

The Master of Magnetism dominates the walls of a scrap metal yard to keep graffiti artists at bay.

This forgotten building was one of the few Philadelphia-area breweries to survive Prohibition.