The main halls of the Outer and Inner Courtyards are arranged in groups of three - the shape of a Qian trigram, representing Heaven. The residences of the inner courtyard are arranged in groups of six - the shape of a Kun trigram, representing the earth.
The sloping ridges of the roofs are decorated with a series of statues. The number of statues reflects the status of the building - a smaller building might have only three or five. The Hall of Supreme Harmony has ten statues - the only building in the country to do so during the imperial era.
The tenth statue, called "Hangshi", is also unique in the Forbidden City.
