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.

A crumbling hospital from the 1850s on Roosevelt Island.

Rippling sand dunes frozen in the Arizona rock.

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

An artsy hidden staircase leads to breathtaking views of San Francisco.

A psychedelic labyrinth on the San Francisco bay.

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

A huge musical instrument played by the ocean.

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

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

Abandoned railway line circling the city of Paris.

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

Try not to get slimed in Tribeca.

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

This dramatic landscape hidden on the Isle of Skye looks as though you've stepped into the magical realm.

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.

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

On Japan's Tashirojima Island, cats are king.

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

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

The only structure left with direct ties to the Salem witchcraft trials of 1692.

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

An emerald-green grotto just a short trip from Austin.