This impressive collection of rare books on ancient mysticism inspired author Dan Brown.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

A curious collection dedicated to human and animal anatomy and pathology.

Founded in the 4th-century, the town of Pernik plays host to the Surva Carnival⁠—a magnificent display of masked Kukeri dancers.

These natural cliffs look like they are a part of an old castle complex.

Rock carving created 1,300 years ago 75 feet off the ground.

Ruins of an early Roman Christian church dating back to the 4th to 5th centuries.

Outstanding, eerie frescoes and decorations fill this 19th-century monastery.

The site of many battles and tragedies, including the 40 maidens who leapt into the sea.

An ancient Thracian city where fire rituals were practiced on the largest cult altar in Southeast Europe.

This historic black and white monastery is one of Bulgaria's architectural jewels.

Bizarrely shaped rock formations in northwest Bulgaria come with equally bizarre legends.

Neolithic burial chambers hidden beside a village school.

This Neolithic-era complex boasts standing stones, a cairn, and the only henge in Western Scotland.

This collection of Neolithic monuments make up one of The U.K.'s richest archeological landscapes.

A rocky outcrop where monks hid their most holy relic while escaping Danish invaders.

A rampant horde of demons smirk and snarl at visitors to this church, home to a rare complete set of medieval-era stained glass windows.

These unknown Bronze Age earthworks are believed to be ancient burial mounds.

Europe's "only museum dedicated to the decapod" is full of quirky and absurdist displays, including one featuring the "famous" Giant Crab of Margate.

Inspired by a dream, a hermit carved out a home in this sandstone bank to live a life of contemplation and prayer.

Long-secret natural history museum, featuring the skull of a "Terror Bird."

A museum and gardens with unusual plants and a history of progressive programming for the blind.

A wonderfully eccentric Victorian-era museum and library.

This captivating Bronze Age timber circle spent centuries concealed by the tides.