As early as the year 1000, a wooden palisade protected the first abbey church from brigands and pirates. In the 13th century, stone fortifications replaced it to protect the sanctuary from armed troops. They were reinforced a century later during the Hundred Years’ War. The Fanils enclosure, the most recent, was built in the 16th century. Built on a rock of barely 960 metres in circumference, isolated by the tide every 12 hours, the ramparts of Mont-Saint-Michel are a technological feat of medieval military architecture.