Each temple built by the ancient Egyptians represented the Mound of Creation, which had risen from the primordial ocean at the beginning of time. In temple architecture, the mound was marked by a gradual rise in ground level between the entrance and the innermost shrine, while the columns of the hypostyle hall represented the first plant life to appear on the mound. Every temple had a sacred lake and was surrounded by an undulating mudbrick wall: it is thought that both these features were intended to represent the primordial ocean from which the mound arose.