The Temple of Heaven is an imperial complex of religious buildings situated in the southeastern part of central Beijing. The complex was visited by the Emperors of the Ming and Qing dynasties for annual ceremonies of prayer to Heaven for a good harvest. 

The Temple of Heaven was inscribed as a UNESCO World Heritage Site in 1998 and was described as "a masterpiece of architecture and landscape design which simply and graphically illustrates a cosmogony of great importance for the evolution of one of the world's great civilizations.

The temple complex was constructed from 1406 to 1420 during the reign of the Yongle Emperor of Ming Dynasty, who was also responsible for the construction of the Forbidden City in Beijing. It is currently located in Dongcheng Beijing, China.

The complex was extended and renamed Temple of Heaven during the reign of the Jiajing Emperor in the 16th century. JiaJing also built three other prominent temples in Beijing, the Temple of the Sun in the east, the Temple of Earth in the north, and the Temple of Moon in the west. The Temple of Heaven was renovated in the 18th century under the Qianlong Emperor.
The Temple grounds cover 2.73 km2 of parkland and comprises three main groups of constructions: the Hall of Prayer for Good Harvests, the Imperial Vault of Heaven, the Circular Mound Altar.

Earth was represented by a square and Heaven by a circle; several features of the temple complex symbolize the connection of Heaven and Earth, of circle and square. The whole temple complex is surrounded by two cordons of walls; the outer wall has a taller, semi-circular northern end, representing Heaven, and a shorter, rectangular southern end, representing the Earth. Both the Hall of Prayer for Good Harvests and the Circular Mound Altar are round, each standing on a square yard, again representing Heaven and Earth. The number nine represents the Emperor and is evident in the design of the Circular Mound Altar: a single round marmor plate is surrounded by a ring of nine plates, then a ring of 18 plates, and so on for a total of nine surrounding rings, the outermost having 9×9 plates.

 According to wikipedia.org