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

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

This one-time health resort was used by aristocrats around the world.

This 13th century Gothic brick castle is the largest in the world by surface area.

This picturesque castle in Poland has a rich history, including a legend that ties it to lost Incan treasures.

A floundering Polish shipyard was once the soul of the Solidarity movement that capsized communism.

These mechanical goats first battled it out in the year 1551, all because of an overcooked deer.

The silly symbol for an underground protest group is now scattered around the city.

A fairytale Gothic castle steeped in Nazi treasure conspiracy theories.

The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

Sitting beneath an unremarkable residential building is a museum devoted to classic Pinball.

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

Tucked away near more famous landmarks lies a statue meant to symbolize the confluence and continuing development of human culture.

Climb around the high waterfalls on series of iron ladders and bridges within the wildest gorge in the Slovak Paradise.

A statue marks the exact spot where The Boy Who Never Grows Up made his first literary appearance.

Some of England's last cave dwellers lived and worked within this huge cave.

A magnificent winding road through a steep valley, with deep natural caverns at the bottom

Semi-precious Blue John stones have been mined in this cavern system for centuries.

The tower was originally used as a chimney for the waste incinerator of St. John's Precinct and Market.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

The heads of two giant mythological water horses honor Scotland's horselord past.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

Protecting the dead from opportunistic body snatchers.