The Château d'If
If this name conjures up images of swashbuckling adventures, extravagent wealth, and breathtaking betrayal, you're on the right track. Castaway in the bay of Marseille, this 16th century fortress-turned-political-prison held enemies of the state—and in the Count of Monte Cristo, one Edmond Dantès. In Alexandre Dumas' novel, this bleak citadel is where Dantès morphs into the mysterious Count to take his revenge. The isolation and narrow cells are enough to turn any man desperate.
Mont St. Michel
This majestic medieval sight off the coast of Normandy never fails to make visitors gasp at its arresting beauty—like an oasis in the salt flats, the almost-island seems to nearly defy gravity with the monasteries, halls, and cottages that cling to it. Used on and off as a house of worship and a convenient prison, the most spine-chilling story is its origin. In a dream, the Mont's founder, Aubert, the bishop of Avranches, was convinced to build this wonder by the archangel Michael when he drilled into the man's skull.
The Arena of Nîmes
The graceful classical arches of this coliseum may have you feeling like you took a wrong turn and wound up in Rome or Andalusia, but we're still very much in France. Nîmes' amphitheater is a vestige from its days as a Roman colony, and it dates to around the same time as the more famous one in Rome. While not spooky on its own, the legacy of the blood spilled here by gladiators and other warriors of the arena is enough to inspire some goosebumps.
The Catacombs of Paris
Perhaps the darkest site in the City of Light is the Catacombs. Created at the turn of the 19th century to make room for the newly dead, the catacombs have served as secret tunnels during WWII, mushroom farms, and a convenient stash for wine bandits. For the many purposes it serves, the catacombs have remained consistently creepy—the bones of some six million Parisians not only rest here, but have been hewn into decorations and support beams.
This hulking Merovingian palace and fortress is today a part of Paris' Palais de Justice (and an anchor for Sainte-Chapelle), but it acted as "the ante-chamber to the guillotine" during the Revolution. Nobles and declared traitors were kept here until they met their fate—the most famous being Marie-Antoinette, whose cell has been memorialized here.