A gravity-defying "devil's bridge" that has a surprising architectural feature for its stability.

Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.

Natural stone arches form a walkable "cathedral" at low tide, then disappear entirely when the water returns.

This abandoned mansion has a window for every day of the year, and is a temple for ghost hunters.

Sanctuary on a ridge near an ancient shrine to a "Black Madonna" built by the founder of Opus Dei.

The corpse bride of Portugal.

Tiny communists hammer away on the Olomouc Astronomical Clock.

Countless stories attempt to explain Poland's mysterious J-shaped trees.

Real bones which are said to have belonged to a Polish dragon.

An underground city of salt.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A house of bones — but nobody is quite sure to whom they belong.

Skulls from the plague of 1656 and World War II bombings are united by a cult dedicated to caring for the ancient dead.

This small chapel is built of human bones and decorated with a golden skeleton.

Bold black and white motifs of life and death add a dramatic flair to this 17th-century crypt.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

A Spanish town built into the cliffs.

Moorish signal station on a stratgic rocky outcrop.

The world's largest wooden structure.

Ancient catacombs form the foundation for this Rococo orgy of a church.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

An honorary saint of the people, Maria Adelaide became an incorrupt corpse, the clothes intact, exhaling “a strong scent of roses.”

The mummified right fist of a 1,000-year-old saint-king sits inside an ornate golden reliquary.

The mummified relic of St. Catherine sits forever on a golden throne.