Before leaving the terrace of the Three Great Halls, you get a commanding view of the Gate of Heavenly Purity facing the 722 foot long Qianqing men Square. This is the demarcation between the Outer Court and the Inner Court or Back Palace. This northern section of the Forbidden City was reserved as the residence for the emperor plus his family and concubines. Gate of Heavenly Purity is perched on a five foot, white marble platform. During the Qing dynasty, several emperors conducted morning court here from 1644 until 1861. This reconstruction from 1655 replaced early versions destroyed by fire.