An abandoned socialist utopia built in the late 19th century.

An accidental trick of light casts the perfect shadow of a pilgrim of the Camino de Santiago against the cathedral wall.

"Alleys of Stone" form natural mazes in Spanish natural park.

This small and often-overlooked museum holds some of Spain's finest artistic treasures.

The world's largest historic armory was established by independent citizens to defend themselves from the wars of larger forces.

Austria's ultra-modern art museum looks like Cthulhu's giant alien heart.

Double spiral staircases are not unheard of, but they are very rare.

This huge metal monument is slowly being stripped to its concrete skeleton.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

A forgotten and crumbling Yugoslav monument to the victims of fascism.

Yugoslavia's biggest underground airport lies in ruins.

An abandoned brutalist monument whose history has been lost to the ages.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

Earth's rocky history has rarely glittered so brightly as it does in this Spanish museum.

Built to power trains, the engines in this building provided the entire city of Madrid with electricity during the Spanish Civil War.

One of Madrid's oldest trees, with a long and colorful history, resides in El Retiro Park.

Strange masks and obscure costumes are housed in this old Madrid corrala.

This postmodern apartment block was designed to be a vertical neighborhood.

This fascinating and poignant museum chronicles every imaginable aspect of Spanish colonialism in the Americas.

This lucky bronze frog was gifted to Madrid by a casino.

A lush indoor jungle fills this bustling Madrid transportation hub.

A Very Low Frequency transmitter you can tune in on your PC.

There are no crying babies in this neck of the woods.

One of the world's few mounted blue whales, its jaws are hinged open allowing visitors to descend into a lounge.