Green labyrinth formed by a karstic maze hidden in a preserved oak forest.

This French castle is said to have once held the Holy Grail but is now a gorgeous mountaintop ruin.

There is a strange little carving of a person seemingly crushed by a pillar behind the remains of St. Thomas Aquinas.

A medieval church built into an ancient cave.

A magnificent Neogothic tomb hides within this Italian fairytale-like forest.

An abandoned 17th-century baroque hunting lodge with a wonderfully strange architectural plan.

The city of Palestrina was built around this magnificent terraced sanctuary dedicated to the pagan goddess Fortuna.

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

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

Mysterious hillside with a continuously burning natural fire.

The world's greatest slide descends 18 stories from this looping mountaintop viewing platform.

A "Titanic" superfan changed his name to Jack and set up this strange shrine to the blockbuster, complete with Korean food and Tarot readings.

A network of hundreds of interconnected wineries in caves hides under the town center.

According to myth, Zeus himself was hidden in this cave to escape being eaten by his dad.

This famous city eluded concrete detection until the early 2000's.

The alleged house of the Virgin Mary is tucked away in a park and nature preserve on Mt. Koressos in Turkey and is holy to both Catholics and Muslims alike.

A spectacular cave and a beguiling lake.

Hidden in a secluded Greek cove is a pristine beach marred only by the rusting smuggler's hulk stranded on its shores.

Cave on extinct volcano, once home to famous mathematician Pythagoras.

Giant marble phalluses on the sacred island of antiquity.

Replicas of Apollo's leonine stone guard cats still line a sacred row in Greece.

This remarkable cave was discovered after a shepherd watched bees enter and exit through a small fissure.

Seventeen oak trees sprout from the roof and walls of this tiny chapel without any visual evidence of roots.

The hallucinogenic center of the ancient world.