A miniature rainforest is growing inside of a Midtown Manhattan office building.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

Abandoned railway line circling the city of Paris.

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

This massive library holds what was once the largest book collection in the world.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

A bizarre house filled with an astounding array of collections.

Manhattan’s Battery Park has a whimsical carousel full of spinning, glowing fish.

High on a hill overlooking Los Angeles lives a world famous, high power conical Tesla Coil.

The legendary building that needed ghostly approval before being built.

Dramatic river bend surrounds a natural red-rocked pedestal.

The installation’s official name, “You Who Are Getting Obliterated in the Dancing Swarm of Fireflies,” says it all.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

An exquisite tunnel of cascading flowers.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

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

An eerie, derelict amusement park in Berlin.

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

Most-visited and most-photographed slot canyon in the American Southwest.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

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