Water came down from the roof through a small drain carved in the outside north wall of the grotto.It was led to a small pool which served to decant it before it flowed into the cistern proper.

• 水从屋顶沿著北边外墙挖的小水管流下来，形成一个小水池为协助它徐缓地流入更适合的贮水槽。