3. Click The Château d'If is a fortress (later a prison) located on the island of If, the smallest island in the Frioul Archipelago situated in the Mediterranean Sea about a mile offshore in the Bay of Marseille in southeastern France . It is famous for being one of the settings of Alexandre Dumas' adventure novel The Count of Monte Cristo . The château is a square, three-story building 28 m long on each side, flanked by three towers with large gun embrasures . The remainder of the island, which only measures 30,000 square metres, is heavily fortified; high ramparts with gun platforms surmount the island's cliffs.