A French chateau, failed utopian community, odd museum, and Stonehenge replica in rural Washington State.

An elevator into the Baltic Sea.

Where manatees are the snowbird vacationers in these balmy Florida springs.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

An unassuming store hides relics of its former life as the jazz club that hosted some of the best black performers of the 1920s and '30s.

A makeshift shrine to the late rock star is still kept up on the nondescript façade outside 1 Logan Place.

This London plaque marks the spot where David Bowie's famous alien made his debut.

This artist's home turned gallery/museum preserves the creator's love of "Eastern" influences.

Public access to clean drinking water was an instant hit among the masses.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

Charles Babbage's proto-computer, painstakingly brought to life.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

"Purveyors of traditional sweets and vintage treats."

Catacombs turned marketplace.

A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

Repository for more than 22 million pickled specimens.

Rebuilt remains of a temple to Roman god Mithras.

In this cobwebbed old operating theater, you can practically hear the screams of the unanesthetized patients.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

The largest of London's subterranean rivers and once a mad, bad center of London life.

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