CAIRO -- The burial chambers of Egypt's 4,500-year-old Chephren pyramid at Giza near Cairo are to reopen to the public on Sunday after 18 months of restoration, AFP quoted the government as saying on Saturday. The monument, the second largest of the trio of great pyramids, will be reopened as part of a rotation program under which the smallest pyramid, Mycerinus, will be closed for a year, Minister of Culture Faruq Hosni said. Three tombs containing colorful wall-paintings of ancient Egyptian life, located in a cemetery next to the largest pyramid, Cheops, are also being opened, custodian of the pyramids Zahi Hawass said in a government statement. The number of tourists allowed to crawl inside the pyramids is restricted to a few hundred a day to limit damage to the walls from humidity caused by their breathing and sweating. Since Chephren was closed in January 1999, a conservation team has removed graffiti and salt buildup from the walls of its chambers and replaced the stairs which take visitors deep inside the pyramid, the statement said.