The Frioul archipelago in the Gulf of Marseilles includes several islands of various sizes, which in ancient times were used as a habitat for a dubious public. By order of King Francis I, in 1524-1531, a fortress was built on one of the small islands closest to Marseille. This is not the only fortification in the archipelago, there are fortifications to protect Marseilles on other, more significant islands, respectively, and the fortresses there are more serious. And the castle of If, according to experts, was built rather carelessly and had no great defense value.→