It is said that the poor builder who was responsible for the final stage of construction was so behind with his work he made a pact with the devil.
He agreed to trade his soul in return for the bridge’s completion. As the last stone was laid the builder pulled a cunning trick, he gave the devil a sieve with which to carry water for the final batch of mortar, and the last stone was never laid. Another version of the legend says that the builder refused to lay the last stone and thereby saved his soul, therefore the bridge was technically never finished.