A view of the excavation at the Lushanmao ruins in Baota District, Yan’an City, Northwest China’s Shaanxi Province. Archeologists estimate the ruins date back approximately 4,500 years and span approximately two million square meters. A larger number of relics made of earthenware, stone, bone and jade have been found over two years of excavation. Zhang Hua, the director of Yan’an City Cultural Relics Research Institute, said the delicate jade items were thought to have been used in worship. The findings also brought the history of the building of Yan’an city 2,300 years earlier.