1. Architectural style: Qianmen Arrow Tower is a typical ancient building in China, which adopts the traditional architectural style of Han nationality, and its architectural form and decorative techniques have strong China characteristics; Zhengyangmen is a western-style building, whose architectural style is influenced by European architecture and has obvious modern architectural characteristics.
2. Function: Qianmen Arrow Tower is mainly used as a symbol and landmark building of the city, and it also has certain defense function; Zhengyangmen, as the gateway of Beijing, has important traffic and military significance.
3. Historical background: Qianmen Arrow Tower was built in Ming Dynasty, which is an important part of Beijing and one of the representatives of ancient architecture in China. Zhengyangmen, built in the Qing Dynasty, is one of the witnesses of China's modern history.