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

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

The lengthy skeleton of one of the tallest Spaniards of all time is on display in Madrid.

This funky former tobacco factory is one of the most striking examples of Madrid's cultural diversity.

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

One of the world's oldest universities houses an incredible collection of anatomical models, mummified body parts, and human bones.

A whimsical brother of the nearby Fallen Angel statue takes the falling part quite literally.

A lush indoor jungle fills this bustling Madrid transportation hub.

Commonly acknowledged as the only public monument to the Devil himself.

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

An ancient Egyptian temple in the middle of Madrid, Spain.

This charming wooden church was disassembled and moved not once but twice before settling in this Prague garden.

This artificial cave looks like something out of a fairytale.

A collection of anatomical samples from one of the first anthropologists to suggest that humans reached North America by crossing the Bering Strait.

The first museum in the world devoted to sexual gadgetry.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Walk through Czech history in Prague's largest graveyard.

A Jenga-style cylindrical tower of books that appears to go on forever.

The hidden lair of an alchemist rediscovered in a 2002 flood.

Macabre astrological automaton clock dating to the late 1400s.

Two stunning 17th-century libraries and a cabinet of curiosities.

This demon atop the Notre-Dame de Paris looks utterly bored.

The video game-themed street art first popped up in the French city.

The final resting place of the "father of special effects."