Together with the islands of Pomègues, Ratonneau, and Tiboulen, the island of If is part of the Frioul archipelago located off the Endoume district in Marseille. With an area of 356,555 sq. ft. (33,125 m²), it extends over 984 ft (300 m) long and 590 ft (180 m) wide at most. Distant of 2.7 miles (4.4 km) by shuttle from the Old Port of Marseille, it emerges to the east of the two main islands of Pomègues and Ratonneau. If Island is almost entirely occupied by the Château d'If, an old fortress built by order of King Francis I, later transformed into a prison in the 17th century and made famous by Alexandre Dumas's novel The Count of Monte Cristo.