The Temple of Heaven is an axial arrangement of Circular Mound Altar to the south open to the sky with the conically roofed Imperial Vault of Heaven immediately to its north. This is linked by a raised sacred way to the circular, three-tiered, conically roofed Hall of Prayer for Good Harvests further to the north. Here at these places the emperors of the Ming and Qing dynasties as interlocutors between humankind and the celestial realm offered sacrifice to heaven and prayed for bumper harvests. To the west is the Hall of Abstinence where the emperor fasted after making sacrifice. The whole building is surrounded by a double-walled, pine-treed enclosure. Between the inner and outer walls to the west are the Divine Music Administration hall and the building that was the Stables for Sacrificial Animals. Within the complex there are a total of 92 ancient buildings with 600 rooms. It is the most complete existing imperial sacrificial building complex in China and the world's largest existing building complex for offering sacrifice to heaven.
In architecture the entire design is symbolic. The southern part of the Inner Temple is square, while the northern part is semi-circular, a pattern representing the ancient belief that Heaven is round and Earth square. The northern wall was built higher than the southern wall, illustrating the notion of Heaven surpassing Earth. Compared to the imposing complexity and intricacy of royal palaces, the altar area here is simple, setting off the vastness of the sky, and the grandeur of Heaven.
In ancient China, odd numbers were regarded as heavenly or as related to the sun. Since nine was considered the most powerful of all numbers, the altar, a three-tiered terrace, was constructed with rings of stone slabs in multiples of nine, and the steps and balustrades are also in multiples of nine. At the center of the top terrace lies a round stone known as the Center-of-Heaven Stone, which has an amplifying impact for speeches made from it.
Three major structures of the altar, namely the Circular Mound Altar, the Imperial Vault of Heaven and the Hall of Prayer for Good Harvests all have round floors and roofs, in accordance with the concept of round Heaven. Deep-blue tiles were chosen to cover these structures so as to harmonize with the blue sky.
The Circular Mound Altar, also known as the Altar for Worshiping Heaven or the Sacrificial Altar, is the place where the emperor worshiped Heaven at the winter solstice. The Imperial Vault of Heaven is the place where the tablets of the gods were kept, surrounded by a circular wall of polished bricks, known as Echo Wall where a person whispering close to the wall at any point can be heard distinctly at any other point along the wall.
In the northern part of the temple, the Hall of Prayer for Good Harvests is a lofty, round structure with triple eaves and a cone-shaped blue-tile roof crowned with a gilded knob. When the hall was built in 1420, the colors of the triple eaves, from top to bottom, were blue, yellow and green, representing the God of Heaven, the emperor, and the common people. In 1752, all the eaves were painted blue. The hall burned down in 1889 after being struck by lightning. It was reconstructed in 1890 and renovated in 1970.
The ceiling of the Hall of Prayer for Good Harvests is painted with an exquisite design of nine dragons, and is supported by 28 wooden columns. The four central columns, called the Dragon-Well Columns, represent the four seasons. They are surrounded by two rings, one inside the other, of 12 columns each. The inner ring symbolizes the 12 months of the year, and the outer, the 12 divisions of day and night according to the old Chinese way of reckoning time. Every year, the emperor led civil and military officials to the hall and prayed for good harvests.
Designed with distinctive compactness and exquisiteness, and decorated magnificently, the Temple of Heaven is a building complex of a beauty rare even among the sacrificial buildings in China and a valuable part of the architectural heritage of the world.
