The courtyard of the ambulatory was completely filled by the core building, a massive 22 m large and 11 m high construction. This edifice, located at the center of the temple complex, was excavated in 1904 and 1905 by Edouard Naville. He reconstructed it as a square structure topped by a small pyramid, a representation of the primeval mount which possibly resembled the superstructures of the royal tombs at Abydos. This reconstruction, supported by H. E. Winlock, was contested by D. Arnold, who argued that, for structural reasons, the temple could not have supported the weight of a small pyramid. Instead, he proposed that the edifice was flat-roofed.