The Iles du Frioul is a collection of 4 islands off the coast of Marseilles. They are Pomègues, Ratonneau, If and Tiboulen. Until the 16th century they were largely uninhabited although visited by passing sailors needing a rest from trade or war. But in 1516, Francois the Ist visited Marseille and decided the islands were the perfect place for a fort to defend Marseille, hence the Ile d'If was developed as a fortress and later, prison.
From the 17th to the 19th century, they were used as a place of quarantine for people suspected of carrying plague or cholera. Sea birds and rare plants thrive on these tiny islands, each about 1.25 miles (2.5km) long, totalling 500 acres (200 hectares), which are sprinkled with the ruins of the old quarantine hospital, Hôpital Caroline and Fort Ratonneau (used by German troops during WWII).
In 1974, the small village of Port Frioul was established as a base for exploring the flora, fauna, beaches and clear-waters of the islands. It has restaurants and around 700 mooring points for boats.
There is a regular ferry service to the Ile d'If. To visit the others look to hiring a private boat, or go by organized tour.