In 1617, the Duke of Guise gave Jean de Bellon the task of building a fort intended to block sea access to Cannes. Constructed between 1624 and 1627 on the site of remains that dated back to Roman antiquity, at the time it was nothing more than a simple fortified house.
These humble origins would be enhanced a few years later by the Spanish who then occupied the islands. Only two years later in 1637 the French took back possession of the island and named the fortress Fort Royal.
At the end of the seventeenth century, the fort became a state prison and continued to grow in size. The prisoners held inside the fort include most notably: the famous, but nevertheless unidentified, Man in the Iron Mask, held for 11 years from 1687 to 1698; Six protestant pastors, imprisoned following the revocation of the Edict of Nantes, from 1689 until their deaths in 1713; Jean-Baptiste Suard, who would become the eternal secretary of the French Academy, incarcerated between 1751 and 1753; The Smala d'Abd el-Kader, from 1843; 600 Austrian prisoners, detained in 1859 after the battle of Montebello; Marshall Bazaine, the only prisoner to have escaped from the Royal fort in 1873, in what legend describes as a fantastic escape and after whom a terrace of the fort is today named.
- Ile Sainte Marguerite