In 552, the Great Wall was built, starting at the northwest frontier, starting from Lishi (离石) and expanding towards west Shuoxian (朔县), with total length of over 400 kilometers. In 555, Emperor Wenxuan commanded to repair and rebuild the existing Great Wall of Northern Wei. Over the course of the year 555 alone, 1.8 million men were mobilized to build the Juyong Pass and extend its wall by 450 kilometres (280 mi) through Datong to the eastern banks of the Yellow River. In 557 a secondary wall was built inside the main one, starting from east of Pianguan (偏关), passing Yanmen Pass, Pingxing (平型) Pass, and continuing to Xiaguan (下关) in Shanxi Province. In 563, Emperor Wucheng built a section of frontier wall along the Taihang Mountains on the border of Shanxi and Hebei provinces. These walls were built quickly from local earth and stones or formed by natural barriers. Two stretches of the stone-and-earth Qi wall still stand in Shanxi today, measuring 3.3 metres (11 ft) wide at their bases and 3.5 metres (11 ft) high on average. In 577 the Northern Zhou conquered the Northern Qi and in 580 made repairs to the existing Qi walls. The route of the Qi and Zhou walls would be mostly followed by the later Ming wall west of Gubeikou. Emperors Emperors family tree See also Buddhism in China Tomb of Lou Rui (570 CE) Notes References Citations Sources Book of Northern Qi. History of Northern Dynasties. Zizhi Tongjian''. External links Dynasties in Chinese history Former countries in Chinese history 550 establishments 6th-century establishments in China 577 disestablishments 6th-century disestablishments in China