The original entrance to the pyramid is on the northern side. Inside the pyramid are three chambers: at the top is the burial chamber of the king (the "king's chamber"), in the middle is the statue chamber (erroneously called the "queen's chamber"), and under the foundation is an unfinished subterranean chamber ("underworld chamber"). Whilst the burial chamber is identified by its large sarcophagus made of granite, the use of the "queen's chamber" is still disputed – it might have been the serdab of the "Ka" statue of Khufu. The subterranean chamber remains mysterious as it was left unfinished. A tight corridor heading south at the western end of the chamber and an unfinished shaft at the eastern middle might indicate that the subterranean chamber was the oldest of the three chambers and that the original building plan contained a simple chamber complex with several rooms and corridors. But for unknown reasons the works were stopped and two further chambers were built inside the pyramid. Remarkable is the so-called "Grand Gallery" leading to the king's chamber: It has a corbelled arch ceiling and measures 28.7 ft in height and 151.3 ft in length. The gallery has an important static function; it diverts the weight of the stone mass above the king's chamber into the surrounding pyramid core.