It was principally notable as the cult center of the sun god Atum, who came to be identified with Ra and then Horus. The primary temple of the city was known as the Great House ( or "Per Aat", "*Par ʻĀʼat") or House of Atum (' or "Per Atum", "*Par-ʼAtāma"; , "Pithom"). Its priests maintained that Atum or Ra was the first being, rising self-created from the primeval waters. A decline in the importance of Ra's cult during Dynasty V led to the development of the Ennead, a grouping of nine major Egyptian deities that placed the others in subordinate status to Ra–Atum. The high priests of Ra are not as well documented as those of other deities, although the high priests of Dynasty VI (BC) have been discovered and excavated. During the Amarna Period of Dynasty XVIII, Pharaoh Akhenaten introduced a kind of henotheistic worship of Aten, the deified solar disc. As part of his construction projects, he built a Heliopolitan temple named "Elevating Aten" (' or "Wetjes Atum"), whose stones can still be seen in some of the gates of Cairo's medieval city wall. The cult of the Mnevis bull, another embodiment of the Sun, had its altar here as well. The bulls' formal burial ground was situated north of the city.