The most significant festival in ancient Sumer involved a symbolic marital union of the Sumerian king and Inanna, the goddess of love. The ritual always took place at the new year. The marriage of the king and the goddess was thought to ensure a prosperous year for all Sumerians.
In ritual ceremonies for the burial of kings, attendants took part in numbers commensurate with the popularity of the king. The attendants would lay the body down and completely seal the tomb. At its opening they would make sacrifices to their fallen king and then bury the entire tomb except for the tops of the walls. Inside the tomb, the king was laid to rest in a brick room in the middle of the structure. Adjacent chambers branching out would hold attendants buried with the king. On a clay floor, people would sacrifice human lives to the king. They would then build a platform on top of the bodies and offer more human sacrifices. As sacrifices continued, the importance of the lives being sacrificed increased until a major sacrifice, such as the queen, was made last. She would get a coffin at the very top of the sacrificial tomb, and a chapel would be built over the whole structure that would indicate the tomb's location.
It is possible that within the Sumerian temples another ritual ceremony may have occurred, in which he who went there to pray before the god of the temple would be able to take the hand of that god. A Sumerian text written in Akkadian, called the "Great Hymn to Nabu," suggests the possibility of such an ancient ritual. In it, the worshiper asks the god Nabu to take him by the hand, exalt him from his low place and give him power.
Another ancient Sumerian celebration was known as Akitu. This was a Babylonian new year's celebration, and honored a god named Marduk, a prince named Nabu and various other gods. It dated to and was rooted in an earlier festival known as Akitisegurku, which was a celebration for sowing barley that took place between March and April.