This abandoned island off the Venetian coast has been a radical monastery, a political prison, and a secret Nazi base.

The marble facade hides a little-known medical museum with early surgical instruments and rare copies of canonical texts.

Thousand-year-old Viking runes adorn an ancient Greek lion at the entrance to the Venetian Arsenal.

Those who own or stay at this 500-year-old, allegedly cursed house often meet terrible fates.

Hanging within this medieval church are the bones of a beast allegedly slain by a fourth-century saint.

100 year tradition of fist fights, marked by marble footsteps.

A sinister pyramid in the Frari contains the heart of the famous neoclassical sculptor.

The plague quarantine island home to the alleged "Vampire of Venice."

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

As can be expected from a centuries old church built in a canal city, the undercroft of this house of worship is beautifully flooded.

Venice's "Island of the Mad."

Go inside to really appreciate this 500-year-old technological masterpiece.

A once grand hotel now sits eerily abandoned in the Catalan countryside outside Barcelona.

Home of modern dancer famously strangled by her own scarf.

The key to turning shifting dunes into the green oasis of Golden Gate Park.

A brooding mansion of clinker brick stands out among the Victorian houses of Pacific Heights.

The remains of a 12th-century chapter house in Golden Gate Park.

Half of a house.

An overlooked and unassuming engineering marvel.

This 19th-century church is now a popular roller rink.

The oldest burial ground in the city, final resting place of city founders, Ohlone natives and murderers alike.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

The one-time watch house for incoming ships at the Golden Gate now stands abandoned and hidden in trees.