These curious caverns have been home to mushrooms, gangsters, and disco.

Funhouse of found art and participatory sculpture.

This large midwestern cavern features impressive rock formations and an underground waterfall.

An architecturally-focused antique shop.

A museum within a museum, devoted to history's most questionable medical devices.

The famed architect designed this Minnesota gas station of the future with a lookout tower.

Half of a waterfall goes into the river while the other half seems to disappear.

This lab's maddening silence is good for business but bad for sanity.

South Dakota's oldest operating brewery is housed inside a historic firehouse.

Yes, this monument is aware that it is about 20 miles away from the actual center of the United States.

This monument remembers one of the manliest men of the frontier who fought a grizzly before dragging himself 200 miles to safety.

An entire city block built completely out of petrified wood.

This geodesic gallery holds a collection of painted spheres that make traditional canvases look lazy by comparison.

One of America’s oldest and spookiest hotels, thanks to the residency of ghosts, dead presidents, and Alfred Hitchcock.

Hidden behind Lincoln's head is a 70-foot-long chamber containing enamel plates documenting American history, sealed in a teakwood box in a titanium vault.

An alchemist's "magic door" stands in the middle of a Roman park.

Pompeii's less famous neighbor is still revealing her secrets.

A submerged archeological park still holds the wonders of a Roman Sodom.

Thousands of well-dressed mummies below a monastery.

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

A 16th-century horror show built in a lovely Italian garden.

No cyclone yet has been able to topple this rugged Indian lighthouse.

This bright pink Gandhi memorial was built so that sunshine hits a specific spot on his birthday.