The ancient city wall of Shouxian in Anhui

The city wall has a circumference of 7147 meters, with a height of 9.7 meters, a base width of 18-20 meters, and a top width of 6-10 meters. The area within the city is 3.65 square kilometers. The foundation of the wall is built with large stones, the middle of the wall is compacted with clay, and the outer wall is covered with oversized blue bricks. The gaps between the bricks and stones are filled with a mixture of tung oil, glutinous rice juice, and lime mortar. On the city wall, there are 'enemy towers' and 'alarm towers', and along the top edge of the wall, there are 'crenels', which are low walls with battlements.