I am working with Babylonian math and some word problems mention an object called a cistern. I looked this up and it seems it can be any tank of water. Some are cylindrical, others rectangular, and others hemispherical.

In the first problem it says "a [rectangular] cistern" so that solves that but in the other it just says a cistern. Should I be assuming a cylindrical shape? I'm not sure what a standard cistern was to the Babylonians.