The Château d'If (French pronunciation: [ʃɑto dif]) is a fortress located on the Île d'If, the smallest island in the Frioul archipelago, situated about 1.5 kilometres (7⁄8 mile) offshore from Marseille in southeastern France. Built in the 16th century, it later served as a prison until the end of the 19th century. The fortress was demilitarized and opened to the public in 1890. It is famous for being one of the settings of Alexandre Dumas's adventure novel The Count of Monte Cristo. It is one of the most visited sites in the city of Marseille (nearly 100,000 visitors per year). Source: Wikipedia (en)