Site of a former hidden treehouse in New Orleans.

Remants of foundations, streets, and streetcar tracks inhabit the cliffs where a landslide occurred in 1929.

The birthplace of an eccentric alchemist and possible inspiration for the fictional reanimator of monsters.

A walk through the historic city center, under the streets of Seattle.

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

One man has carved a number of natural New Mexico caves into psychedelic sandstone temples.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

An enormous, inside-out glass globe built in 1935.

An Australian lake whose pink hue defies scientific explanation.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

The world's only museum devoted to the wonders of fluorescence.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

The ghostly remains of an accidental sea.

A swing to dangle you off the very edge.

The old Niles Canyon Aqueduct in the San Francisco Bay Area is a bemusing and secret trail through nature for wayward travelers.

A massive underwater sinkhole made famous by Jacques Cousteau.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

Hot springs monkey spa in the middle of Hell's Valley.

The abandoned zoo enclosures offer a perfect place to experience the other side of the bars.

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

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

A fiery crater has been burning in the Karakum Desert since 1971.