UNESCO-protected ancient burial ground.

The ceiling of Prohodna Cave in northern Bulgaria affords a peek at the sky via two deity-sized-eye-shaped holes.

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

A spectacular Bulgarian cave resembling a devil's head with a waterfall rushing down its throat.

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

Ancient human remains unearthed around the iconic monument.

Under a church hides a forgotten 13th-century ossuary containing the remains of around 2,500 people.

The walls of this medieval church are covered with perfectly preserved frescos, including a pristine example of the Dance of Death.

It's possible to walk inside one of the largest Neolithic tombs in Britain.

You can crawl inside this atmospheric 5,000-year-old tomb.

An existential riddle in the world's largest ancient castle.

The sanctuary holds what was once believed to be the saint's incorruptible tongue.

This renaissance château was home to an infamous witch hunter who sent a hundred suspected witches to their deaths.

Bullet holes in the church wall are a reminder of the violence that followed the assassination of a high-ranking Nazi officer.

A cheeky architectural easter egg.

Unique house covered in a nightmarish mural of demons, ghosts and monsters.

A controversial artwork draws attention to the dark history of Prague's "Suicide Bridge."

The soulless eyes of 82 bronze children stare on forever in remembrance of a horrifying World War II massacre.

This charming wooden church was disassembled and moved not once but twice before settling in this Prague garden.

These 17th-century mummies are no longer naturally preserved, but remain on display today.

Monument to a suicide protesting the Soviet invasion.

Increasingly decayed figures stand as a powerful reminder of the human costs of Czech Communism.

Synagogue built from the stones of Solomon's temple contains the golem of Prague.

A saintly relic hidden in a Prague church basement.