Archaeologists have discovered sections of the Great Wall in a valley of northwest China's Ningxia Hui Autonomous Region, a former museum curator said on Tuesday. The 20-meter long wall was found in a valley of Nanchangtan Village, Zhongwei City. It is believed to be part of the Great Wall built during the Qin Dynasty (221 BC-206 BC), said Zhou Xinghua, former curator of the Museum of Ningxia Hui Autonomous Region. It consists of three sections, with one section constructed with stones. It is five meters long, three to four meters wide and six meters tall. The other two sections are 10 meters and five meters long respectively. Zhou said to prevent foreign invaders from crossing the Yellow River when it was frozen, the Qin state, which defeated other powers during the Warring States Period (475-221 BC) and later established the Qin Dynasty, built great walls along the valley beside the Yellow River. According to historical records, the newly found wall remains are believed to have a history of over 2,470 years. "It proves that the Great Wall was built in the valley with mountain stones, and needs better protection owing to its great historical value," Zhou said. The Great Wall was listed as a world cultural heritage site by UNESCO in 1987. The central government spent more than 500 million yuan (about 80 million U.S. dollars) to finance the protection of the wall during the 11th Five-Year Plan (2006-2010).