The Great Pyramids were built during the Old Kingdom

Pirámide de Menkaura
Originally uploaded by almadrid

Stunning advances in architecture, art, and technology were made during the Old Kingdom, fueled by the increased agricultural productivity made possible by a well developed central administration.[26]

Under the direction of the vizier, says Wikipedia, state officials collected taxes, coordinated irrigation projects to improve crop yield, drafted peasants to work on construction projects, and established a justice system to maintain peace and order.[27]

With the surplus resources made available by a productive and stable economy, the state was able to sponsor construction of colossal monuments and to commission exceptional works of art from the royal workshops. The pyramids built by Djoser, Khufu, and their descendants are the most memorable symbols of ancient Egyptian civilization, and the power of the pharaohs that controlled it.

Along with the rising importance of a central administration arose a new class of educated scribes and officials who were granted estates by the pharaoh in payment for their services.