The Tour du Fanal is an old round observation tower more than 98 ft (30 m) high, intended to spot and be visible to merchant ships at a distance of 12.4 mi (20 km). Located at the western end of the rampart of the current Fort Saint-Jean on the site of a ruined watch house, it was built by the masons Bœuf, Gay, and Alluys at the request of Marseille shipowners. A first white fixed light was lit at the foot of this tower on July 15, 1837, before being replaced by a red, scintillating light on June 5, 1912.