This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

Deep underground, the rusting remains of a German water pumping station from World War II.

Colorful power station with a chimney equipped with a gallery for exhaust monitoring equipment.

This former railway facility is the oldest in Slovenia, and now houses a museum showcasing the history of steam locomotives.

This was the second largest mercury mine in the world and one of the oldest preserved mine complexes in Europe.

A relic from the Industrial Revolution got a second life as a contemporary performing arts space.

Slovenia's first mosque is a striking mix of Islamic and modernist architecture.

A beautiful drive through the foot of the Alps traces the path of 15th-century Turkish raids.

A crumbling World War I fort that is reached through a series of concrete tunnels.

An otherworldly alpine pasture with its own unique microculture that recalls Middle Earth.

The walls of this medieval church are covered with perfectly preserved frescos, including a pristine example of the Dance of Death.

This abandoned Slovenian military barracks has become a punky-political art squat.

A miniature train-ride through Slovenia's largest cave system.

This deserted town in the hills of Croatia’s "party island" may have a scandalous connection to King Henry VIII.

This work of art is considered the world's longest mosaic.

This ancient Roman aqueduct once funneled water to Diocletian's palace.

Maze-like streets filled with vibrant murals draw visitors to this Istrian town.

A unique two-level bridge designed to honor a king.

Trimmed trees grow alongside the graves like topiary tombstones.

Inside this small chapel tucked away in the forest is one of the most well-preserved Danse Macabre frescos.

This only museum in the world dedicated solely to mushrooms.

This 15th-century church houses priceless works of art from a range of Croatian artists.

This abandoned Croatian stronghold never saw a great deal of conflict but it is still a beloved relic nonetheless.