This ancient Irish religious site is covered in ancient carvings, many of which have barely aged.

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

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

A unique bridge with an equally unique view.

This marvelous array is one of the largest collections of mechanical instruments in Europe.

The last bastion of Roman presence north of the Alps looms over a German town.

Every hour the doors open to reenact the legend of the heroic mayor who saved his town by drinking a gallon of wine.

Horrifically creative torture devices and shame punishments line the walls of this chilling museum.

The fairy tale castle of the “fairy-tale king,” this was also the inspiration for Disney’s “Sleeping Beauty.”

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

A famed artist's inspiring work of peace and tolerance.

Tiny castle in the middle of the Rhine made you pay to pass.

A memorial for a young woman and her ghost, which are claimed to have caused countless deathly shipwrecks.

This fountain of a little boy that spits on passersby at erratic intervals is a town icon.

The historic building has preserved human organs, unusual hexagrams, and scars from a political assassination.

Step inside an ancient beehive tomb built for a mysterious cult hero.

The historic tower houses of this nearly abandoned Greek town have been compared to the spikes on an iguana's back.

This town named for the ancient God of War is home to fewer than a thousand people, but it's the birthplace of the Greek Revolution.

This wrecked ghost ship has been rusting on a Greek beach since the 1980s.

The ruins of an abandoned medieval city where the last Byzantine emperor was crowned.

A quirky bookstore hidden beneath a sea of whitewashed Greek villas.

Where commuters walk through remnants of an ancient Greek necropolis.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.