Tombelaine is a granite island with an area of 9,39 acres (3.8 ha). Some 147 ft (45 m) high, it extends in the middle of the bay, 1,86 miles (3 km) from Mont-Saint-Michel. Already housing a church that welcomed pilgrims since 1137, the rock received a fort built by Philippe Auguste in 1204. During the Hundred Years' War, the English conquered all of Normandy and settled in Tombelaine in 1356. They wished to carry out attacks on Mont-Saint-Michel, which still resisted them. They never succeeded, and Tombelaine became French again in 1451. In 1666, Louis XIV razed the fortress and all the constructions covering the rock, today a leading ornithological reserve.