A DIY art gallery/music venue/lecture hall dedicated to video game culture.

Slyly buy a shake in the Parker Meridien lobby.

The name of this famed hospital was once a byword for the horrors of medical and psychiatric care.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

Jesus' footprints and the first catacombs in the world.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

The yawning maw of this pagan visage is said to bite off the hands of liars.

The underground sanctuary of a mysterious ancient cult.

Architectureal fantasy quarter of Rome.

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

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

The remains of a British railway rusting in the jungle mist of a Brazilian mountainside.

A self-explanatory attraction allows fans to respectfully remember and honor a comedy legend.

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

A solitary tree has grown up all alone on Lake Wānaka, backdropped by the beautiful Southern Alps.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

Oh, just a motel on the edge of the desert decorated with thousands of clowns conveniently located next to an abandoned graveyard.

The oldest hotel in the world has been operated by the same family for over 1,300 years, even catering to samurai.

An uber-secure, windowless tower of doom in the center of Manhattan is an NSA spyscraper.

This hidden stream beneath Indianapolis makes an appearance in the best-selling novel "Underground Airlines."