An Austrian house of bones filled with hundreds of intricately painted skulls.

The great Danube river starts here.

The only remaining collection of flayed figures made by French "madman" Honoré Fragonard.

A spectacular Bulgarian cave resembling a devil's head with a waterfall rushing down its throat.

More than half of this Indian palace is drowned but it looks all the more spectacular for it.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

Thousands of exquisitely carved stone water storage wells, hundreds of stone steps fill this exquisite medieval stepwell.

This abandoned fort is said to be the most haunted place in India, so much so that entry is prohibited after sunset.

Centuries-old bridges grown from tangled roots.

The second-deepest known cave on Earth, hidden in an extremely remote mountain region.

This vast, water-filled underground labyrinth can only be toured by boat.

This beautiful system of tunnels built into natural rock serves as a centuries old plumbing system.

Hydraulic systems in an ancient underground Iranian city.

At the foot of a waterfall lies a peaceful swimming lagoon and evidence of over 60,000 years of human habitation.

A serpentine highway twists and turns over the treacherous Norwegian Sea.

A stunning silver lining to global warming's gloomy cloud.

An intricately carved Viking church overlooks a glistening fjord.

The burning of this 12th-century church kicked off a campaign of Norwegian Black Metal terror.

Walk behind a 50-meter-high waterfall.

Walk 2,300 feet above the ground on the "Troll's Tongue."

This giant boulder is pinched over a 1000-meter abyss by two mountains.

From Coke II to Google Glass, this exhibit features some of the most spectacular commercial flops.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

A small man-controlled waterfall powers an Art Nouveau elevator and is accessed via narrow gauge, solar-powered tramway.