The most famous extant altar should be Beijing's Tian Tan (Temple of Heaven), or the Temple of Heaven, located on the east side of the front gate in the south city of Beijing. The Temple of Heaven is a world-level artistic treasure, its artistic theme sings the praise of the supreme "heaven", and all artistic techniques aim to play up the solemnity and nobility of the heaven, gaining extremely outstanding achievement.

It is the place where emperors of the Ming and Qing dynasties (1368-1911) worshipped the heaven and was built in the 18th year (1420) of the reign of Ming Emperor Chengzu. As Chinese emperors called themselves Tianzi, or the son of heaven, they had to cede supremacy to the heaven in terms of abiding. The altar, in a plane round shape, called Huanqiu Tan (Circular Mound Altar), was rebuilt in the 17th year (1752) of Qing Emperor Gaozong. The Qinian Hall (Hall of Prayer for Good Harvests) was rebuilt in the 16th year (1890) of Emperor Dezong.

The Temple of Heaven has an area of 273 hectares, which is five times the size of the Forbidden City, with a layout in two squares one inside the other. Two walls divide the ground into the outer and inner parts. The outer wall is 6,416 meters long and the inner wall is 3,292 meters long. The northern part of the outer and inner walls is a semicircle and the southern part of them is square, declining from north to south to symbolize the traditional belief that Heaven was high and round and the earth was low and rectangular.

Walking eastward from the front (west) gate, within the inner wall there is a Zhaigong (fasting-palace) in the south for the emperor to fast and bathe before worshipping. Further east is a north-south vertical axis formed by the main buildings. The five-meter-high Circular Mound Altar is in the south with a three-layered stone terrace. Within the Beiyuan courtyard of the Circular Mound Altar is a round hall or the imperial vault where the spirit tablet of the heavenly god is placed. Going further north, one can reach the Hall of Prayer for Good Harvests via Danbi Bridge.

The Temple of Heaven uses ecological artistic technique to give prominence to the theme of "heaven". For example, the density of structures is very small, covered by large tracts of pine and cypress trees, creating a strong atmosphere of solemnity and nobility. The inner walls are not in the middle of the area enclosed by the outer walls, but rather they shift toward the east, the vertical axis of the cluster of buildings also shifts eastward for about 200 meters, thus prolonging the distance from the front gate. This helps people feel they are removed farther from man's world and nearer and nearer to the gods.

The Circular Mound Altar is crystal white, setting off the holy, pure, empty and bright "heaven". Its two-layered enclosed walls are only a little more than one meter high before the tall, large round terrace, so as not to block the visual line. During the Ming and Qing dynasties in early winter the emperor would come to this mound to pay homage to heaven and pray for peace and a good harvest. The 400-meter long and 30-meter wide Danbi Bridge, and the courtyard of the Hall of Prayer for Good Harvests, also stand above the surrounding ground, for the same effect. The round Hall of Prayer for Good Harvests is 24 meters in diameter, its three-layered eaved pinnacle covered with green glazed tiles. Under this is a six-meter three-layered, white stone round terrace with a total height of 38 meters. The green roof seemed to merge with the blue sky. All these are designed to create a close relationship between man and heaven.

The Temple of Heaven widely uses symbolic and metaphor techniques to play up the theme. For example, in many cases, a round plane is used. The Circular Mound Altar uses the number 9 or the multiplication of 9 to symbolize "heaven". The Hall of Prayer for Good Harvests uses numbers related to the solar terms of agriculture.

Heart of Heavenly Stone

The Heart of Heavenly Stone placed in the center of the top tier of the Circular Mound Altar. Around it there are nine circles, each with nine stones, altogether 3,402 pieces. They are of identical size and appearance and put closely together. They have remained intact during the past several hundred years. When people stand on the Heart of Heavenly Stone and shout echoes will be heard.

Echo Wall & Nine-Dragon Cypress

The circular wall surrounding the Imperial Vault of Heaven is 193.2 meters long, 3.7 meters high and 0.9 meter thick. If one speaks against the wall at one end, another can hear his voice at the other end of it. The Nine-Dragon Cypress outside the Echo Wall was planted 500 years ago. Its twining branches look like nine dragons.