In ancient times, the Qiantang River was always flooded, so local parents in Hangzhou mobilized people to build seawalls along the river, from Wangjiangmen to Haining, and at the same time, build castles along the river to inform the tide or flood, which is somewhat similar to the beacon tower of the Great Wall.

From Fort One to Fort Twenty-three, due to historical changes, the Qiantang River has also been diverted, and some place names are no longer used. For example, Erbao is usually called Jinjiang Village, Shibao is called Sanjiao Village, and Yibao is already Qianjiang New City.

Fortresses 3, 4, 5, 6, 7, 8, 9, 12, 14 are still in use. Fort 23 seems to be still in use in Haining, but after 14, it went out of Hangzhou. I don't know.