Archaeologists working in northern Peru have discovered a spectacular tomb complex about 1,000 years old. The complex contains at least 20 tombs, and dates from the pre-Inca Sican era. Among the discoveries are 12 "tumis", ceremonial knives which scientists have not been able to study in a burial site before, as well as ceramics and masks. The Sican culture flourished from approximately AD 800-1300, one of several metalworking societies which succumbed to drought and conquest. Archaeologists working on the project say the find will help them understand details of the culture. "It is a religious city, a sacred settlement, and at each excavation site is a cemetery," Izumi Shimada told Peru's El Comercio newspaper. "That tells us that Sican was a very organised society." Professor Shimada, based at the University of Southern Illinois in the US, has been excavating Sican sites for a quarter of a century. The latest dig was performed in conjunction with the Sican National Museum. The burial site sits on Peru's northern coast, near the town of Ferrenafe. Discoveries in the tomb complex include tumis formed from an alloy of silver, copper and gold; masks, breastplates and ceramics.