The astronomical clock in Besançon Cathedral is one of the most extraordinary mechanical devices in France. Built in 1860 and housed in the choir of the Cathédrale Saint-Jean, it occupies a space roughly the size of a wardrobe but contains 70 dials and some 30,000 moving parts, all operated by gravity-driven weights and gears without any external power source.
The clock displays the time in Besançon and twelve other cities simultaneously, along with the phases of the moon, the position of the sun in the zodiac, tidal information, and a perpetual calendar. Guided tours are the best way to understand what you are looking at — the mechanisms are explained clearly and the sheer ambition of the machine is genuinely impressive. The cathedral itself, with its Gallo-Roman column from an earlier temple still standing in the transept, is also worth a longer look.