Dome

Archery tower from the west; Zhengyangmen (popularly called Qianmen, "Front Gate") was first built in 1419 during the Ming Dynasty and once consisted of the gatehouse proper and an archery tower, which were connected by side walls and together with side gates, formed a large barbican. The gate guarded the direct entry into the imperial city. During the Boxer Rebellion of 1900, the gate sustained considerable damage when the Eight-Nation Alliance invaded the city. The gate complex was extensively reconstructed in 1914. The Barbican side gates were torn down in 1915. At 42 metres high, the Zhengyangmen gatehouse was, and remains, the tallest of all gates in Beijing's city wall. The Zhengyangmen is situated on the central north-south axis of Beijing. The main gateway of the gatehouse is aligned with the Tiananmen Gate. The kilometer zero point for highways in China is located just outside the Zhengyangmen Gate. It is marked with a plaque in the ground. Source: Wikipedia; http://en.wikipedia.org/wiki/Main_Page (accessed 6/23/2013)