A large in-ground water retention basin background), measuring approximately 16x9 m and constructed of thick volcanic rock and marine sand mortar walls over 1 m wide and 2 to 3 m high, dominates the northern end of the mill area. An opening at the bottom of the deepest corner of the basin transferred water into a smaller and deeper adjoining water reservoir (foreground) with a metal tube drain imbedded in its west wall. The smaller reservoir is located close to the stone wall with a tunneled flue connected to the smokestack.
