The form of a Sumerian temple is manifestation of Near Eastern cosmology, which described the world as a disc of land which was surrounded by a salt water ocean, both of which floated on another sea of fresh water called apsu, above them was a hemispherical firmament which regulated time. A world mountain formed an axis mundi that joined all three layers. The role of the temple was to act as that axis mundi, a meeting place between gods and men. The sacredness of 'high places' as a meeting point between realms is a pre-Ubaid belief well attested in the Near East back the Neolithic age. The plan of the temple was rectangular with the corners pointing in cardinal directions to symbolize the four rivers which flow from the mountain to the four world regions. The orientation also serves a more practical purpose of using the temple roof as an observatory for Sumerian timekeeping. The temple was built on a low terrace of rammed earth meant to represent the sacred mound of primordial land which emerged from the water called dukug, 'pure mound' (Sumerian: du6-ku3 Cuneiform:) during creation.