9 is an ordinary number, but for the ancient Chinese philosophers, it has rich connotations. People can find interesting answers from ancient architecture of the Temple of Heaven in Beijing.

　　 The Temple of Heaven was an architecture of complex for the emperors of the Ming and Qing dynasties to pray in spring for a good harvest and offer sacrifices to heaven in winter.

　　There is a sacrificial altar called Circular Mound Altar in the Temple of Heaven.The number “9” can be found here and there in the architecture. For example, each of the three tiers of the staircases made of white marbles has nine steps. When you walk up the Circular Mound Altar, along the steps, you’ll find a round stone slab at the center of the altar, which is also the only round stone in the altar. It’s called Taiji Stone, or the Stone of Heaven Center

　　 Looking around the Taiji Stone, the first circle around the Circle of Mound Altar consists of nine fan－shaped stones； for the second circle, 18 stones； third circle, 27 stones and so on. All of these round stones slabs for every circle is the multiple of “9” . The number “9” has a special philosophical meaning, because the heaven is “Yang” or masculine while the earth is “Yin” or feminine. “Yang” is represented by an odd number of the figures from 1 to 9. It implies reverence for heaven which is most lofty. Therefore, number “nine” has a deep philosophical meaning. It hints something rational. And emperors who called himself the son of heaven would naturally offer sacrifices to heaven and communicate with heaven in a world composed of the nines.

　　 Therefore some people said that the Circular Mound Altar include endless numbers. For instance, the area of the up tiers of the Circular Mound Altar is 9 “Zhang” in diameter. The total number of the diameters of the three tiers of the Circular Mound Altar is 45 “Zhang”, which not only is the multiple of 9, but also symbolizes the supreme position of the emperor and the heaven.

　　In the remote historical periods, there are also sacrificial buildings like the Temple of Heaven in Beijing. Archeologists once found sacrificial altar in the ruins of Hongshan culture. The altar was built by ancient men with stones. So the origin of building an altar to offer sacrifices to heaven and the introduction of its philosophical meaning can date back more than five to six thousand years.

　　 Every year on the winter solstice, the emperor would hold grand rituals to offer sacrifices to heaven. The Temple of Heaven was once a mysterious place for such ritual ceremonies. The philosophical meaning of number 9 in ancient China was reflected in the figurative architecture. It shows the understanding and worship of ancient Chinese people for heaven and nature. Here the ancient culture and the ancient architecture were combined into one.