Major advances in architecture, art, and technology were made during the Old Kingdom , fueled by the increased agricultural productivity and resulting population, made possible by a well-developed central administration. [26] Some of ancient Egypt's crowning achievements, the Giza pyramids and Great Sphinx , were constructed during the Old Kingdom. Under the direction of the vizier , 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