The base of S is a circular disk with a radius r. Parallel cross sections perpendicular to the base are squares. Find the volume of the solid.

Does somebody have some good graphing software who can help me visualize this thing? In my mind, circular disk is also called a cylinder, and you can get a square from a cross section depending on where you cut it, but only if you cut it in exactly the right place. Clearly I am missing something.

Thanks.