Vienna's underworld of tunnels and subterranean rivers made an iconic appearance in a 1949 Orson Welles film.

A two-way chairlift system between Zugliget and the highest point in the city.

A 19th century artistocrat's mansion, turned into a library, hidden in a modern library.

An 11th-century medieval castle cascades over the town of Numão.

The best Tiki bar in Las Vegas.

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

This futuristically sylvan church is a glass-enclosed marvel of modern architecture.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

This Boston medical museum features the skull of the famous medical case of Phineas Gage.

Surprisingly aquamarine waters fill deep lakes formed at the end of the last ice age.

A 14-foot monument marks the resting place of two of the town's earliest residents—and one unknown soldier.

Thomas Jefferson's estate is home to hundreds of varieties of historic fruits and vegetables.

An enormous warehouse filled with parade floats collected from over 50 years of patriotic celebrations.

This Virginia railway overpass is said to be haunted by a serial killer in a rabbit costume.

This 29-ton granite ball spins around at the slightest touch thanks to a scientific phenomenon.

This museum devoted to the gothic author holds such interesting ephemera as his socks and walking stick.

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

This small town Texas cemetery is said to be the burial site of a UFO pilot who crashed in the 1800s.

Back in 1952, you could get a mushroom cloud chaser with your atomic cocktail.

An ordinary pond with fish from out of this world.

A 70-foot-deep ice cave formed by lava from Mt. Fuji on the edge of Japan's "Suicide Forest." 

A garden in Lisbon filled with giant porcelain creatures.

Abstract marble carving for an 8.5-pound rock.

It may look like no more than a full-scale model, but every part of this full Space Shuttle stack had a working role in aviation history.