Ratonneau Island is part of the Frioul islands in the bay of Marseille. Approximately 1.5 mi (2.5 km) long for a width of 0.3 mi (0.5 km), it served as a quarantine site for foreign boats after the construction of the Caroline Hospital (on the left) between 1823 and 1828. Used until 1941, the hospital nicknamed the wind hospital welcomed travelers in the event of a suspected epidemic. One of Marseille's natural advances on the sea, the island also had a military vocation illustrated by the building and maintenance of various fortifications over the ages.