In 1524 Gabriel de puy, a French military engineer built the Tour Gabriel to finish
the Enceinte des Fanils, the walls built to protect the storerooms of the Abbey.
The ramparts were planned with an eye to the latest developments in the field of
artillery, which made it possible to shoot in all directions in the least possible
amount of time. In the 18th century, when the military vocation of Mont Saint Michel
had been superceded, a windmill was set up on the top of the tower.
Then, in the 19th century a lighthouse was added to act as a beacon for navigation
of the Couresnon.