The latter are closed at the mouth by great round stones in form of a mill-stone, pierced in the centre. This second opening is itself closed by another stone, which is taken away when the water is drawn. This system of closed wells and cisterns by means of a stone is of extreme antiquity.
Great round stones, shaped like millstones with holes in the middle, seal the openings at the mouths of these structures. The secondary openings are then closed by additional stones that are taken away to access water. This method of sealing wells and cisterns with stones dates back to very ancient times.