Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

Hellam Township is reputed to feature seven remote gates, which when passed through in the right order, open an entrance to hell.

An abandoned cemetery lies in ruins as the surrounding forest swallows it whole.

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

A toxic ghost town sitting atop a massive coal fire.

The whole world in one water tank.

Deep scars on the earth left by the Ice Age.

An unoccupied lighthouse encased in layers of ice from the waters of Lake Erie.

These sub-farmland caves are home to a majestic stalactite known as the "Crystal King."

Take a drunken tour inside the world's largest known geode.

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

This maze-like slot canyon is a unique gem within an already fascinating geological area.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

The perfectly named cave drop is the deepest in the continental United States, almost matching the height of Seattle’s Space Needle.

A curious whirlpool formation supposedly capable of entangling or engulfing branches, tree trunks, or whole rafts full of hapless tourists.

Bad farming practices caused this unnatural natural wonder.

The only Florida state park with publicly accessible caves.

Where monkeys run wild and the humans are caged.

Disney World's very first waterpark is now an abandoned ruin being reclaimed by the swamp.

A secret, rocky playground hidden amongst the plain white beaches of the Florida coast.

The scuba diving training facility was named for the steam that rises from the cave's chimney.

A theme park featuring a replica of Noah's Ark built to the measurements specified in the Bible.

Moonbows over Kentucky.