The Temple of Heaven, an architectural wonder, is a complex of three main structures, the Hall of Prayer for Good Harvests (Qinian Dian), the Imperial Vault of Heaven (Huangqionyu) and Circular Mound Altar (Huanqiu Tan). Its symbolic importance is the continuity of the mandate of heaven for the ruling imperial house whose emperor has to perform some Zhou Dynasty ritual at the winter and summer solstices in the Confucian tradition.
The area was built by the Ming Yongle Emperor with twice the area of his own palace and based on Chinese numerology and geomancy (fengshui). The four gates point to the directions of the compass. The north end of the compound conforms to heaven as a semi-circle, and the south end to earth as a square. The last ritual to be performed here was by the General Yuan Shikai in 1915 when he tried to establish a dynasty which collapsed with his death a year later.
The Hall of Prayer for Good Harvests was originally built in 1420, but it was burnt down by a fire in 1889. It was then rebuilt based on its original plan. The hall is entirely of wood without the use of any nail. The roof is made of glazed blue tiles converging onto a golden central point without beams or spars. It is supported by 28 pillars brought over from the southern province of Yunnan. There are four main pillars representing four seasons, followed by two surrounding rings of 12 pillars each. The inner ring represents the months of the year and the outer the time of day according to the Chinese calendar. At the middle part of the floor is the Dragon Phoenix, the imperial symbols. From this room the Emperor would pray to heaven for good harvests.
To the south is the Imperial Vault of Heaven, built in 1520 and restored in 1752. It houses the tablets for ceremonies. Further south is the circular brick wall called Echo Wall (Huiyin Bi). On can whisper at one part brick wall and the echo will be transmitted clearly round the wall. The Circular Mound Altar built in 1530 and reconstructed in 1749 after a fire. It has three open air marble tiers representing Man, Earth and Heaven and was the site where the Emperor would offer sacrifices for good harvests.