It is the largest surviving wooden structure in China. It rises about 30 meters above the level of the surrounding square. It has a coffered ceiling decorated with a coiled dragon from whose mouth comes a set of metal balls called the "Xuanyuan Mirror". This is a reference to the Yellow Emperor (Huang Di), a mythological Chinese ruler. Legend has it that the metal spheres will fall and crush anyone who usurps the throne.
During the Ming Dynasty, the emperor sat here to discuss state affairs. During the Qing Dynasty, this hall was used for ceremonial purposes such as coronations and imperial weddings.
