The assignment was to build a new structure to replace the former temporary structure wich was in very poor condition and a new antechamber. The antechamber, needed to control the thermal exchanges, was tougt like a new “perfect rock” among the others existing ones. The main concerns of the structure to allow visitors inside the cave, was to be able to run a clean and dry construction, considering the impossibility of using construction techniques that would require welding and / or in situ concrete and the use of enduring materials capable of withstanding the passage of time in a particularly hostile environment. We decided that this structure should be opaque and black in sharp contrast with the light color of the limestone cave.