Introduction to the Water Release City Gate: The Nine Gate Great Wall has nine water release city gates. On the city gate is a huge water city bridge across the Jiujiang River estuary. There are sieges on both ends of the bridge, just like a bridgehead. Each of the nine water gates is 5 meters wide, 7 meters high, and the crenels are 10 meters high. Each of the two sieges has 7 caves, with bricks inside and stones outside, tall and majestic, very spectacular.