Fort de Saint-Priest, Military fortification in Saint-Priest, France

Fort de Saint-Priest is a Séré de Rivières fort built between 1887 and 1890 on the Belle Étoile site at 256 m altitude. Its main barracks is sheltered by a concrete shell 2.5 m thick at the top, poured in one piece and covered with a metre of sand. The trapezoid enclosure is surrounded by ditches, and a 4 m high defensive grille covers the side facing Lyon.

The fort was built between 1887 and 1890 as part of Lyon's second defensive ring protecting the region. Its purpose was to monitor the Isère plain and guard the Grenoble railway line.

The fort takes its name from the Belle Étoile locality in Saint-Priest. Its grounds were marked by 21 octagonal stone boundary posts, each engraved on top with the direction of the next post, and the site was split into three servitude zones: one banning all building except the fort, one allowing construction that would be demolished on alert, and one forbidding changes to the terrain and roads.

Visiting is easiest during Heritage Days when guided tours and photo exhibitions about the fort's past are available. The site sits on a hilltop, so wear comfortable shoes for walking the grounds.

The powder magazine held 71 tonnes of black powder and was built against the barracks rather than away from it, a choice made possible by the arrival of melinite in 1884, a less dangerous explosive to store. It was lit by oil lamps placed outside behind thick layers of glass.