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

The legendary building that needed ghostly approval before being built.

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

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

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

A 140-year-old castle with underground caves hidden in San Francisco.

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

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

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

Dramatic river bend surrounds a natural red-rocked pedestal.

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

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

These old stone ruins in the Oregon wilderness were once bathrooms and are steeped in legends of murder.

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

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

The neon signs from Las Vegas' past find their final resting place at this unusual graveyard.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

On the Oregon coast there is a natural hole that seems to be draining the sea.

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

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

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.

Rippling sand dunes frozen in the Arizona rock.

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.