Adjacent to the great court are the ruins of dummy chapels that originally surrounded the Heb-Sed Court that commemorated festival(s) held during the king's reign. This very ancient festival, dating at least to the time of Narmer, was celebrated during a king's thirtieth regnal year and every third year subsequently. (Some pharaohs cheated, as one might suspect, and held their festivals earlier. In the 19th dynasty, Ramses II, who lived to be 96 and ruled most of that time, held Sed festivals every two years after his initial 30-year celebration.)
The festival apparently had at least two major purposes. The main one, from the king's perspective, was to celebrate his long tenure as divine monarch. But of equal importance was celebration of the union of Upper and Lower Egypt, which suggests that it may have been begun by Narmer. The king presented offerings to various gods and was crowned with the double (white and red) crown of Upper Egypt and Lower Egypt. And then supposedly he ran four times around the court to prove that he was still able to rule. That may have been problematic after being king for 30 years!
On to Giza