An existential riddle in the world's largest ancient castle.

The oldest garden in Prague, once part of an medieval orchard.

The mystery of the Putim Ossuary involves a tricorn hat.

Underneath the city that invented pilsners are a series of historic tunnels that have been storing beer for centuries.

Increasingly decayed figures stand as a powerful reminder of the human costs of Czech Communism.

A turn of the century building boasting some of the most beautiful art nouveau architecture in Prague.

The soulless eyes of 82 bronze children stare on forever in remembrance of a horrifying World War II massacre.

This unusually shaped mountaintop tower looks like a UFO floating over the city.

Street artists transformed an abandoned air vent into the beloved Star Wars robot.

Mysterious painted skulls in Moravia.

The deepest sinkhole in Central Europe comes with a grisly tale and an unusual nickname: “The Stepmother Abyss.”

A spiral staircase twists to the top of this unusual Czech lookout tower.

This former quarry is now a picturesque gorge that hides a sunken lake.

A saintly relic hidden in a Prague church basement.

The tunnel's elegant proportions keep you snug with no claustrophobia freak-out.

This artificial cave looks like something out of a fairytale.

A bust of Franz Kafka spins in pieces, reflecting the writer's inner torment.

A mocking tribute to the past and modern leadership of Prague.

The world's greatest slide descends 18 stories from this looping mountaintop viewing platform.

Bohemian paradise covered in majestic forests.

Buried five stories underground, this Soviet bunker is packed with gas masks and Cold War paraphernalia.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

Thirty creepy ghosts now inhabit this decaying 14th-century church.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.