Ratonneau Island is one of the islands in the Frioul archipelago. It is relatively long and thin, approximately 2.5 km long. It is connected to the island of Pomègues. An interesting fact is that an ancient Roman fleet was anchored on the island around 49 BC. Later, (1720) the island was used to quarantine foreign sailors, particularly for cases of cholera and leprosy. Around 1820, trade and transport through Marseille experienced an unprecedented boom. The need for an extension of the port was evident. It is in this context that a yellow fever epidemic broke out in 1820. Thus the municipality decided to build a hospital (Hôpital Caroline, 1828) on the island of Ratonneau, and to link it to the island of Pomègues by a dam.