The Tour du Fanal, also known as the Tour Ronde (Round Tower), is a former watchtower of more than 98 ft (30 m) intended to see and be visible to merchant ships at a distance of 12.4 mi (20 km). It was built in 1644 at the request of Marseille shipowners. Located at the western point of the rampart of the current Fort Saint-Jean on the site of a ruined watch house, it was built by the three masons Bœuf, Gay, and Alluys. A first white fixed light was lit at the foot of the tower on July 15, 1837, before being replaced by a red, scintillating light on June 5, 1912. The fortress' construction by the Chevalier de Clerville and Vauban under Louis XIV aimed to keep the city under control after a local rebellion (1658-1660) against the royal power.