This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

A terrific purveyor of natural history objects and curios.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

The only one of New Hampshire's original 14 World War II watchtowers to survive in near-original condition.

Maybe the only missile installed in a public park, this Cold War leftover was one of the first to carry a nuclear warhead.

Once the future of underwater combat, this old sub is now open for visitors to muck around in.

The largest arcade museum in the world chronicles the golden age of video games which ended promptly in 1987.

These towering spires and glowing walls are carefully crafted from hundreds of thousands of icicles.

Even Henry David Thoreau found this glacial pothole irresistible.

This narrow canyon has been carved by the river over thousands of years into spectacular and curious forms.

Ruins of the elaborate house where the enigmatic costume designer threw glamorous parties for New York's theatrical elite.

Overgrown ruins of a turn of the century island fort that sees very few visitors.

Colorful clay cliffs tower over an unofficial nudist beach on Martha's Vineyard.

It was an experiment to prove that glacial boulders and rocks can be used in constructions and dwelling.

A spooky and decrepit mental health facility is slowly being replaced with newer digs.

The railroad tunnel nicknamed the "Bloody Pit" for taking the lives of hundreds during its construction.

This railroad tunnel was once the longest in Massachusetts.

Locals purchased this abandoned quarry in order to make sure it continues to be overgrown.

The bears may be gone, but their old cages can still be found.

This miniature feudal castle was built on a whim to honor a US Navy pioneer.

The ruins of a Massachusetts prison farm can still be found crumbling the woods of a state park.

Site of a famous 19th-century transcendentalist utopian community, now abandoned.