Sacred stone at Heliopolis that symbolized the Primeval mound and perhaps also the petrified semen of the sun god Re-Atum, when he self-copulated and brought things into being. Utterance 600 of the Pyramid Text says:

‘O Atum-Khoprer, you became high on the height, you rose up as the bnbn-stone in the Mansion of the Phoenix at On’

The stone served as the earliest prototype for the obelisk, and possibly even the pyramid. In recognition of these connections, the gilded cap-stone placed at the very top of each pyramid or obelisk was known as a benbenet. The original stone at Heliopolis was believed to have been the point at which the rays of the rising sun first fell, and its cult appears to be dated back to the First Dynasty.