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

Museum dedicated to the terror regimes of Hungary.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Bell tower juts out from a village buried under a lake.

Pilgrimage site for star-crossed lovers.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

Water and windows define this defensive Italian well.

This picturesque Umbrian city has a subterranean side that has long remained hidden.

Medieval town turned hippie commune, once home to the secret foreskin of Jesus Christ.

Largest necropolis in the Mediterranean.

Breathtaking and huge 430 year old maps of Italy.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

The yawning maw of this pagan visage is said to bite off the hands of liars.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

A Nesting Doll of Churches.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

An alchemist's "magic door" stands in the middle of a Roman park.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Stone memorial that's said to predict the death of the pope and the site of the Cadaver Synod.