Legend has it this 11th-century castle was paid a visit from the devil.

Fighting the British and making game shows for over 150 years.

French commune at the heart of conspiracies.

These medieval ruins have survived since the 12th century, even providing shelter from the Nazis.

The ruins of a medieval castle linked to the murderous French lord that inspired the famous legend of Bluebeard.

The 16th-century church was kept in its ruined state as a reminder of the casualties of World War I.

An ancient ossuary in Rouen.

Despite centuries of architectural innovation, this French castle is being built like it's the 13th century.

Underneath a chalk hill in France lies what Hitler hoped would be the underground launching base for a devastating new weapon.

These crumbling Nazi artillery bunkers are now fair game for massive graffiti projects.

The Church of the Annunciation was carved into the face of a cliff, just like the rest of the town of Haute-Isle.

The spiral staircase hidden inside this giant Parisian column was likely built for Catherine de Medici's astrologer.

The post-apocalyptic remnants of a bucolic town ruined by a plane crash.

The great Italian Renaissance painter was laid to rest here in the Chapel of Saint-Hubert.

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

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

An ancient monastery, a locked room, and a mysterious book heist.

Historic medieval fortified city in southwest France.

The largest underground church in Europe.

A subterranean shelter remains intact under a busy Paris railway station.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

One of the greatest maze designer’s greatest mazes.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.