This seemingly unremarkable boulder is said to bear the hoofprint of the devil himself.

One of New York's best collections of pinball is hidden in a secret bar in the back of this laundromat.

Sniff the Titan Arum's rotting flesh.

Just your average Marie Antoinette–themed speakeasy in an abandoned 19th-century subway tunnel.

Architectural monsters are devouring this palace's every door and window.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

A forgotten "city of water" underneath the famous Trevi district.

A collection of objects supposedly singed by the hands of souls in purgatory.

Jesus' footprints and the first catacombs in the world.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

The underground sanctuary of a mysterious ancient cult.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

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

An indigenous ethnobotanist runs this brunch spot celebrating Australia’s native flavors.

Outdoor art exhibition made of classic Tetris pieces.

It's said to be one of the most significant collections of contemporary Chinese art in the world.

The statue honors an adventurous seafaring cat.

A boardwalk winds through this sliver of coastal nature hidden within Sydney.

One of Australia's largest secondhand bookstores.

A collaboration of art and ornithology mourns the calls of Sydney's lost birds.

A century-old hotspot for jazz, frequented by everyone from Charlie Chaplin to Al Capone.

A Bibliophile's Dream.

A lush green oasis in the middle of Chicago.

This morbid, delightful curiosity shop offers everything from animal bones to human teeth.