A fortified structure at No.55 Ha Pak Nai, which is a declared monument owing to its connection to the revolutionary movement of modern China under the leadership of Dr. Sun Yat-sen. Hsing Chung Hui (Revive China Society) members, who were KMT, stationed at Lower Pak Nai for preparation of overturning the ruling of Qing authority and conducted bomb tests. (Luo 1971:37) The structure was built by a core member of Hsing Chung Hui named Tang Yam-nam around 1910. It was the only solid evidence correlating the 1911 revolution and its movement leader Sun Yat-sen and his comrades. The structure served for the surveillance across the Deep Bay coast under the Qing authority.