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

This abandoned coliseum was intended to be a grand Nazi rallying ground before it was halted at the end of the war.

A castle from the Holy Roman Empire that hosts traveling youth... in its stables.

Small museum dedicated to one of the founding fathers of modern astronautics.

This incredible stone temple is a monument to death, victory, and fantasy architecture.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

The deepest metro station in the world.

A reconstructed medieval gateway that was the magnificent entrance to the capital city dating back to 1037.

This hanging crocodile is thought to be the "dragon" that once plagued a Czech city.

A peculiar clock commemorates a historic victory won by ringing the noonday bell an hour early.

Europe's second largest ossuary wasn't discovered until 2001.

A church of bones, decorated with 40,000 human skeletons.

This short bridge is the only thing connecting a tiny Irish island to the mainland.

Northern Ireland's Brobdingnagian stepping stones.

The ruins of this medieval castle in Northern Ireland have inspired artists from C.S. Lewis to Led Zeppelin.

This controversial Irish show cave is home to a massive formation known as the Great Stalactite.

A hugely vast Irish landscape of barren rock that stretches for miles.

This Irish show cave is said to have been the site of a Viking massacre that claimed 1,000 lives.

A rocky Irish outcropping with a history of wealth, conflict, and ruin.

See some of the world's greatest racing horses at this idyllic thoroughbred breeding facility and garden complex.

This ancient Irish tower could easily have stood in for Rapunzel's prison.

Amidst the bustling streets of Dublin, there is a hushed garden that is dedicated to "All those who gave their lives in the cause of Irish Freedom."

One of Ireland's most infamous prisons for rebels including men, women and children.