Pont Valentre

The striking Pont Valentré in Cahors, France, was built in the 14th century to be its own fortress, with three towers where the enemy could be attacked from above. However, the massive bridge took 70 years to complete from 1308 to 1378 and never saw combat, although its arduous construction lead to a legend of a deal with the devil.

These "devil's bridges" were not at all uncommon in medieval times, and like most this has a story of soul-selling and outwitting Satan. Supposedly the builder found that he was woefully behind building the bridge (hopefully not the same man who had been slaving on it for seven decades), and made a pact with the devil to trade his soul for the bridge's completion. However, he gave the devil a sieve with which to carry water for the final batch of mortar, and the devil of course couldn't do it, so the bridge was technically never finished. Naturally, Satan was angry, but his best idea of revenge was to break a stone off from the central tower's corner, and remove it each night that it was replaced.

It is this story that was relayed to architect Paul Gout when he was doing his 19th century restoration to explain why there was a stone missing. Inspired, he had a stone sculpture made of the devil showing him pulling a stone from a corner of the tower. He still lurks there today. 

A museum in a former pumping station near the bridge acts as a museum on its history, and as a bonus you can view old pumping machines through a glass window in the floor.