The Hydrostructure

In the west side of the outer enclosure wall, there are brick remains of a structure different from all the other buildings. The brick structure is in fact a small pool from which nine waterways extent beneath the wall and end in a huge brick pool outside it. The entire structure is made of brick with bitumen and plaster mortars to be water resistant.   

Figure 1: The position of the hydrostruture towards the ziggurat of Chagha Zanbil, by Mehrdad Misaghian

Figure 2: The hydrostructure; outside the wall

Figure 3: The hydrostructure; inside the wall

Figure 4: The hydrosructure; outside the wall

Ghirshman believed this structure was a type of water refinery which purified the stored water outside the enclosure wall then, by applying the rule of communicating vessels, sent it to the internal pool through canals and provided water supplies for the city residents.
Later studies suggested that this structure could have been a drainage system for the city’s surface water flows. It would dispose rainwater to the outside of the city.
There is some evidence of two other similar structures outside the enclosure wall as well. However, the ruins are so damaged that it is impossible to reconstruct them.