was built by King Khufu the most powerful ruler of the Old Kingdom. In the largest of the pyramids a system of tunnels was put in place to deter thieves from robbing the tomb. Sources suggest that until the ninth century AD the pyramid remained sealed untouched by robbers, however these intruders also imply that once in the King's chamber they saw the mummy had been taken and the sarcophagus opened. Tombs were ransacked for their valuables but also for their original primary purpose. Once robbed, an empty tomb could be used as a burial place for another mummy, which is exactly what happened in the smallest of the pyramids of Giza. Tourism Most of the tombs are not open to the public (18 of the tombs can be opened, but they are rarely open at the same time), and officials occasionally close those that are open for restoration work. The number of visitors to KV62 has led to a separate charge for entry into the tomb. The West Valley has only one open tomb—that of Ay—and a separate ticket is needed to visit this tomb. The tour guides are no longer allowed to lecture inside the tombs, and visitors are expected to proceed quietly and in single file through the tombs. This is to minimize time in the tombs and prevent the crowds from damaging the surfaces of the decoration. In 1997, 58 tourists and four Egyptians were massacred at nearby Deir el-Bahari by Islamist militants from Al-Gama'a al-Islamiyya. This led to an overall drop in tourism in the area. On most days of the week an average of 4,000 to 5,000 tourists visit the main valley. The West Valley is much less visited, as there is only one tomb that is open to the public. See also Valley of the Queens – Nearby burials of queens and offspring of kings. Royal Wadi and tombs – Burial place of Akhenaten and his royal family. Naqsh-e Rostam – Persian "Valley of the Kings" royal tombs. Ming and Qing Imperial Tombs – Royal tombs of the Ming and Qing Dynasties. Sacred Valley (Peru) Burial place of Genghis Khan – An undiscovered place of burial of Genghis Khan and his royal family. Valley of the Kings (Tibet) References Sources – Details of all the major tombs, their discovery, art and architecture – Covers the history of the exploration of the Valley in