The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

The ruins of an ancient island city built atop a coral reef in the South Pacific are spectacular and strange enough to have inspired H.P. Lovecraft.

An abandoned set from the 1980 film "Popeye," claimed and repurposed as a theme park by creative locals.

The randomness of this wall of lava lamps helps encrypt up to 10 percent of the internet.

The garage at the childhood home of Steve Jobs was a hangout for the founders of Apple, even if they never built computers there.

In its continuing quest to recreate famous parts of the world in miniature, China now has its own ghost Paris.

The world's first hotel built in an abandoned water-filled quarry.

The busy transport hub is home to the tallest airport slide in the world.

A Singapore shrine to an unnamed German girl who has become a local deity.

This psychedelic tourist trap is a leisurely descent into madness.

Legend tells how a Spanish soldier disappeared from this isolated sentry box without a trace.

This foolish Victorian sea fort was converted to a deluxe hotel.

Once the most densely populated place in the world, this island is now a ghost town.

An elevator into the Baltic Sea.

This famed marionette theater and museum is bursting with imaginative string puppets.

A surprisingly detailed model of one of the most powerful telescopes in the world.

A graveyard and memorial chapel for victims of leprosy.

A university observatory dome painted like the beloved "Star Wars" robot.

One of the most easily accessible examples of the rare 1960s UFO houses.

Enter the cabin of a life-sized Hindenburg replica.

Hamburgers are intensely proud of their tunnel beneath the river.

Thousands of flowers create enchanting pink tunnels over the city streets.

It's always summer at the beach inside this former airship hangar.