The subterranean connecting galleries, ammunition magazines, usine and barracks are arranged in a branching pattern.

Four observation posts are associated with Roquebrune, including the Abri Est de Mont-Gros and the Observatoire Croix-de-Muratoire.

[7] Block 3 is essentially the same as the large artillery casemates built by CORF for the main Maginot line in northeastern France, with 75mm guns on the upper level and 81mm mortars firing upwards out of the pit in front of the guns.

The block is sunk into the ground, compared to the more typical batteries in the Alps, which were usually built into the side of a cliff or rock wall.

[1][4][5] The observatory Mont-Gros de Roquebrune 43°45′58″N 7°26′35″E / 43.76611°N 7.44306°E / 43.76611; 7.44306 is an observation block intended to spot the fall of shot for Ouvrage Mont Agel, and is more closely associated with that fortification.