Introduction to the fort: In 1816, the Qing government built a circular fort on each of the north and south banks of Dagukou. The fort is made of wood inside and green bricks on the outside with white ash grouting. It is about one foot and five feet high, nine feet wide and six feet deep. This is the earliest fort in Dagukou, built as solidly as a mountain. By 1841, the Dagu Fort had built 5 large forts, 12 earthen forts, and 13 earth forts, forming the Dagu fort group, and a complete military system had taken shape.