Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

An overlooked monument to the celebrity gangster who helped put the sin in Sin City.

A rare example of World War I trenches from the British front.

Brazil's only museum dedicated to the art and evolution of tattoos.

An abandoned quarry hides an open-air gallery of huge sculptures, some made from the rubble of 9/11.

Trimmed trees grow alongside the graves like topiary tombstones.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

A once drab public housing estate is transformed into a colorful gallery of trompe l’oeil murals.

A bike train runs along a disused railway line through the tranquil French countryside.

This remote research station sits amid the second-largest ice sheet on the planet.

A former prison complex now displays a historic collection of inmate artwork.

Iceland's only steampunk shop imagines a retro-futuristic world that never was.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

This vintage animatronics show is the Vegas version of a walk through the woods.

The secret medieval communication system will whisk your words above the noise of the crowd.

The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

Legend has it a commoner volunteered to be buried alive in the foundation so that the great fortress could be built.

Crouch down, stretch tall, and be sure to flail your legs to pay homage to the Monty Python classic.

The island residents are known for taking their quirky sense of humor with them to the grave.

Its front wall is striped with a menagerie of fantastic beasts and magnificent monsters.

The steepest classic funicular in the world glides along a dizzying incline.

The world's newest astronomical clock is also its most accurate.

This strange moor has a song written about it, Bronze Age carvings, and an alien sighting.

The floor-to-ceiling collection in an old factory is a unique alternative to stuffy galleries.