Part of the extensive necropolis of Memphis is located near the modern suburb of Cairo named Giza. There are mastabas here from as early as the 1st Dynasty, but the area is mainly famous for the three pyramids from the 4th Dynasty and their surrounding mastabas for members of the royal family and high officials. After Sneferu had built the first true pyramid in Dahshur, his son Khufu built his tomb in Giza, the largest known pyramid, constructed of more than 3 million blocks of limestone and originally completely covered in a smooth layer of white limestone from Tura. The pyramid has an unfinished underground room, usually regarded as the original planned burial chamber; after changes to the plan, two further burial chambers were constructed in the superstructure, usually called the King's Chamber and the Queen's Chamber. Both rooms are supplied with upward sloping shafts, previously considered to be ventilation shafts; nowadays an astronomical purpose is assumed. In 1993 a mobile camera was sent into one of these shafts, which resulted in the discovery of a closed door leading to speculations concerning an as yet unknown fourth chamber. Further investigation in 2002 showed that in fact there is only a small space behind this door-panel, followed by a second stone barrier. Close to the pyramid of Khufu are the remains of his mortuary temple, linked by a prossesional way to a now lost valley temple. There are various large pits intended for boats, in two of which boats have actually been found. Nearby is the tomb of Hetepheres, the mother of Khufu; there are also several subsidiary pyramids, regarded as being intended for queens. The most southerly of them became a cult area for the goddess Isis from the Third Intermediate Period on. Khephren built the second Giza pyramid. Although it is slightly smaller, it appears to be larger because it is built on a rise in the plateau. A processional way runs from this pyramid to a well-preserved valley temple made of granite. Next to it is the Sphinx of Giza. Because of its location next to Khephren's valley temple and processional way, it is assumed that the Sphinx was carved by this pharaoh and displays his portrait. The third, much smaller, pyramid is that of Mycerinos. The famous statues of this king, triads with Hathor and various nome gods and goddesses, were found in his mudbrick valley temple.