A 17th-century doorway in a small Sabine village is a portal into the mysteries of alchemy.

The history of occult science is turned into a creepshow at this lurid Prague tourist attraction.

A museum of alchemy and a basement laboratory all housed in an ancient building in a Gothic tower.

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

The hidden lair of an alchemist rediscovered in a 2002 flood.

The birthplace of an eccentric alchemist and possible inspiration for the fictional reanimator of monsters.

A large measuring stick marks the lowest point of a country that is partially under sea level.

These mysterious ruins are hidden amid this sleepy coastal city.

The pretty iron lamp is a reminder of the architecture underneath London's streets.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

Now home to a drinking establishment, this building has a macabre history.

The largest stone circle in the world has ended up bringing up more questions than it has answered.

Fantastically decorated underground chambers built in the 1760s.

This historic franken-chapel is the oldest wooden church in the world, at least part of it.

The history of this famed tree ranges from an 18th-century highway robber, to the Scout Association.

This crumbling 14th century chapel became so unstable the roofing apparently collapsed during a wedding ceremony, narrowly missing the curate's head.

A witch wreaks ruinous revenge on this ancient church with her "enchanted leg."

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

An eclectic treasure trove of maritime marvels.

A swamp that was the site of prehistoric water burials also managed to preserve its corpses for millennia.

Invading U.S. troops were first seen from this now-abandoned tower, leading to the Spanish-American War.

North Carolina's only restored fort from the French and Indian War.

A stone pillar commemorates the surrender of the extraordinary Apache leader.