Dagu Fort is located by the Haihe River estuary 60 km southeast to the city. An important coastal fort, it was built during the reign of the Ming Emperor, Jia Jing. During the Opium War it was expanded and five big forts and 20 smaller ones were constructed. All of these were dismantled when the Eight-Power Allied Forces invaded China. Today there are only two, one on the southern southern bank and the other on the northern bank. In 1988 Dagu Fort was listed as an important historical site, repaired and placed understate protection. It was opened to the public in June 1997.