Final answer:
The Great Pyramids in Giza were built primarily from cut limestone during the Old Kingdom of Egypt; with key parts such as the burial chambers incorporating granite to protect them from robbers.
Step-by-step explanation:
The Great Pyramids in Giza, Egypt were built during the Old Kingdom of Egypt and consist primarily of cut limestone. These colossal structures were part of a mortuary complex that served as burial places and memorials for the Pharaohs Khufu, Khafre, and Menkaure. The largest of these, the Great Pyramid of Khufu, is constructed from approximately 2.3 million stone blocks, each weighing an average of 2.5 tons, meticulously carved and transported from nearby quarries to the construction site. While the underlying core of the pyramids comprises cut limestone, some components such as the burial chamber and the access point's sliding block system were made of granite, renowned for its hardness and durability. Subsequent pyramids in later dynasties, such as those during the Middle Kingdom, would at times employ mud brick in their cores, but the grand pyramids at Giza from the Old Kingdom are distinguished by their solid limestone construction.