The encased skull that is widely believed to belong to St. John the Baptist.

Tables of secondhand books fill the inner courtyard of this 17th-century stock exchange.

A chapel on a volcanic core, marking the end of a successful journey.

This ancient theater was once the home of fierce gladiatorial battles.

A medieval church with largest and oldest collection of Renaissance frescoes in France.

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

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

This medieval tower is all that remains of the castle where Joan of Arc was held before being burned at the stake.

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

Science fiction's grandfather has a fittingly marvelous tomb.

The largest underground church in Europe.

Historic medieval fortified city in southwest France.

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

Ancient paintings known as the "Sistine Chapel of Cave Art."

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

An icy lake tucked among jaw-dropping alpine panoramas.

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

This salt marsh in Southern France is as pink as the flamingos that inhabit it.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

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

One of the most historical literary characters continues to stroll his hometown.

Hidden in the garden of physicist Erwin Schrödinger's house is a life-size figure of a cat from his famous thought experiment.