Why is the quadrangle called Sihe?

Siheyuan, also known as Siheyuan, is a traditional quadrangle-style building in China. Its pattern is a quadrangle with houses on all sides, which usually consists of a main room, an east-west wing and an inverted room. The courtyard is surrounded in the middle from all sides, hence the name quadrangle. Siheyuan has a history of at least 3,000 years, and there are many types in China, among which Beijing Siheyuan is a typical one. Siheyuan is usually inhabited by extended families, which provides a relatively hidden courtyard space relative to the border between China and Shanxi. Its architecture and pattern reflect China's traditional hierarchical thought and the theory of Yin-Yang and Five Elements.