From the publisher's website:

Mesopotamia was home to many tribes and many golden ages as each tribe had its season in the sun. During its season, a tribe would start new temples or continue working on temples begun by other tribes. Thus, with the help of various tribes, the temples grew more and more beautiful and eventually reached so high they seemed to touch the sky. The temples of these master builders took peoples’ breath away, but natural and man-made disasters could bring the temples down. When this happened, the craftsmen began anew, moved to work on other temples, or just went ho me. Even with such setbacks, the temples continued to grow toward the sky as the players worked to complete these monuments. There are several ways to win, but all are based on the total number of temple layers a player has built.