The port entrance is guarded by the Fort Saint-Jean, a 13th-century command post of the Knights Hospitaller of St. John of Jerusalem; some ruins remain, along with a tower built in the mid-15th century by René I of Provence. The extant fortress, dating from the 17th century, was part of a nationwide system of defenses. The other side of the harbour entrance is occupied by Fort Saint-Nicolas. In the harbour itself lie the Frioul Islands, on which the city has developed a large centre for water sports.
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