The outer city wall, called the "peripheral wall" (邊牆; Biān Qiáng) or "pass wall" (關牆; Guān Qiáng), was actually a rammed earth rampart built in 1680 to expand the urban area outside the inner city. It was almost round in shape, standing at a height of 7.5 chi (around 2.7 metres or 8 feet 10.3 inches) and an overall length of 32 li and 24 bu (about 20.7 kilometres or 12.9 miles), and also had eight towerless gates known as the "peripheral gates" (邊門; Biān Mén). The corresponding inner and outer gates were linked by roads that intersected within the inner city in a "#" pattern around the Mukden Palace.