Beautiful carved tunnels.

For hundreds of years, automatons moving to metallic music have been marking the passage of time.

The fantastic architectural models of a French traveler.

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

Ghosts of France's colonial past.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

A Gothic cathedral created from volcanic rocks.

The largest underground church in Europe.

A 14th century bridge built as a fortress, where the devil lurks on one of its towers.

A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

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

A bathhouse from the second Islamic Caliphate decorated with frescoes of constellations, pleasure gardens, and naked ladies.

An ancient capital city that dates back 3,000 years old and harbors many surprises.

A more chill but no less fascinating version of the famous ancient archeological site.

The tallest freestanding structure in the United Kingdom.

What was once England's second-richest abbey is now a haunting ruin.

A 17th-century church is nestled within the walls of a 15th-century ruin.

A striking 500-year-old mansion provides an unexpectedly sublime home for live deer and a menagerie of exotic stuffed animals.

Constructed from recycled wrought iron railroad tracks, it's been described as the most beautiful seaside pier in England.

The intended purpose of this unfinished Elizabethan building remains a mystery.

An abandoned 18th century manse looks like something out of an Indiana Jones movie.