The Low Battery of Petit Vallon (1880 m a.s.l.) is a late 19th century (1890) work armed with 4 guns of 12 G.R.C. Ret placed on barbette pitches placed on staggered floors and with the fire mouth facing Mount Janus. The Battery consisted of a barracks located at a lower level than the firing areas, which was intended to house the forty men who made up the battery operation. The barracks had a single floor in which there were the soldiers 'dormitory, the kitchen and the officers' rooms and was supported by a notable buttress with 2 brick arches; particular of the barracks were the stone and brick finishes of the doors and windows. Next to the barracks there was the room of the artillery warehouse and climbing on the rocky spur above it was possible to reach the guardhouse and the barbette pitches for the guns. From the guardhouse, a small building, one starts climbing up to meet the battery barracks, in perfect condition, which once housed up to forty men. A little further up there are the stands for the guns of the battery located two by two at different heights; from the guardhouse there is a test tunnel that connects it to the ammunition room and to the powder magazine (which are thus located below the shooting stands, connected with some goods lifts).
The Low Battery was connected by a military mule track to the defensive guardhouse of Claviere and to the High Battery, located higher up along the mule track.