Tung Chung Fort
Time Out says
A declared monument in Hong Kong, the Tung Chung Fort dates all the way back to 1832. It's been used for different purposes since then, including as a police station and a school. A visit to the fort will have you picturing yourself in a bygone era, complete with an ancient Chinese fort and Qing-era cannons. For the history buffs, be sure to make a second stop to the nearby Tung Chung Battery.