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

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

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

A huge musical instrument played by the ocean.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A psychedelic labyrinth on the San Francisco bay.

An eccentric home in Sicily turns heads on a regular basis.

Behind medieval walls in a corner of bustling Palermo is a breathtaking former mosque once inhabited by a wolf-taming hermit.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

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

The anatomical-pathological collection of a man who changed surgery.

This mosaic-lined medieval church was built by the world's first admiral and still holds mass in ancient Greek.

Haunting graffiti left by prisoners of the Spanish Inquisition.