It is here, at Fort Royal, that you will find the Cannes Sea Museum. The island has actually been inhabited since the 5th century BC and the Romans constructed buildings there around the 1st century AD. In September 1635, during the Army of Thirty Years with Spain, a Spanish fleet of thirty or more arrived in front of the Lérins Islands and delivered thousands of Spanish soldiers and six guns.
A year and a half later, the French recovered the Lérins Islands and began to fortify them. Over the next 100 years, many plans to strengthen and improve the defenses of the islands were drawn up, but it was finally decided that any effective defensive position on the island would actually become a liability if an enemy invaded again. and took control of these improved defenses.
In 1685 the fort was converted into a prison and it was here that two years later, in 1687, the "Man in the Iron Mask" was imprisoned for a time.