The remains of the second-oldest zoo in Europe can be seen within these library gardens.

This sweet-toothed bear searching for snacks has been a symbol of Madrid for decades.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

A shining memorial to a Belgian hero is said to bring luck to anyone who touches it.

Meet the bronze beloved pet to a family of famous peeing statues.

It's believed that the dead were once taken out of houses through these now walled-up doors.

If you ever wanted to touch a medieval mercenary’s three testicles, look no further.

An abandoned mine now resembles a post-apocalyptic landscape of derelict buildings and blood-red pools of water.

An underground spring in a labyrinthine cave system, decorated with stalagmites and stalactites.

Considered the birthplace of the Copper Age and Bronze Age, the river is tinted red from 5,000 years of mining.

The world's largest wooden structure.

The facade of this 16th-century building is decorated with carvings of 300 seashells.

A hidden medieval crypt where a famous legend says the devil used to teach black magic.

The Cathedral of Salamanca has a number of unusual carvings but none so surprising as a modern astronaut.

An Antoni Gaudí masterpiece in Astorga.

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

Christ's blood allegedly preserved in a Belgian town.

Inside this former medieval prison is a collection of objects designed to inflict unbelievable pain and suffering on the human body and mind.

A beer pipeline runs beneath Bruges.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

Climb inside an iron crystal magnified 165 billion times its normal size.

A little sculpture with a large wardrobe.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."