Reservoirs of the Plaine Saint-Denis (here, the smallest tank), located under the France stadium are one of the largest type of construction. It can hold up to 165.000m ³ of water. The irregular shape of the pillars is due to the construction technique by molding (digging the soil, concrete injection and clearing the land around the pillar).

A forest of pillars in the lower level of the quarry of Port Mahon.

Pillars of consolidation.

Some pillars in the mass, in the ring quarry.

A pillar in the quarry of Bazemont.

Pretty pillars in the underground quarry Keppler at Mery sur Oise.

The forest of pillars in the quarry of Herblay.

The construction of houses above the underground quarry requires new pillars of consolidation.

This pillar is thin, although it is cut in the ground.

Those wood pillars are useless now...