It may not be common knowledge among Western visitors that the number "nine" carried a special significance in old China. Ancient Chinese regarded odd numbers as masculine and even numbers as feminine. "Nine", the largest single digit number, was taken as representing the "ultimate masculine" and was, therefore, symbolic of the supreme sovereignty of the emperor. For this reason, the number "nine" (or its multiples) is often employed in palace structures and designs.
A noticeable example is the number of studs on palace gates. The studs are usually arranged in nine rows of nine each, totalling eighty-one. This is even true of the marble gates of the "underground palace" of the Dingling Mausoleum in Beijing: 81 (9 x 9) studs were carved out of the stone. If the visitor goes to the Temple of Guan Yu in Luoyang, he will also find on the red gate nine rows of nine wood studs each. This was because Guan was given posthumous honours of an emperor.
Ancient palaces generally consisted of nine courtyards or quadrangles; so does the Temple of Confucius in Qufu, Shandong Province - a magnificent architectural complex worthy of an imperial household and testifying to the importance attached to the great sage by the courts of various dynasties.
The buildings of the Forbidden City of Beijing are traditionally measured as having a total floor space of 9,900 bays - some even say 9,999 bays, which may be an exaggeration. The picturesque towers guarding the four corners of the palace compound have each 9 beams and 18 columns, and the three famous screen walls (in Datong and Beijing) have nine dragons on each.
There is a seventeen-arched bridge in the Summer Palace of Beijing. This, too, has much to do with "nine". Count the arches from either end, and you will find that the largest span in the middle is the ninth.
An extreme example of the "game of nine" is perhaps the Circular Mound Altar (Huanqiutan) in the Temple of Heaven. Site for the Ming and Qing emperors to worship Heaven, the altar is in three tiers. The upper terrace is made up of nine concentric rings of slabs. The first ring or innermost circle consists of nine fan-shaped slabs, the second ring 18 (2 x 9) slabs, the third 27 (3 x 9)... until the last or ninth ring, made up of 81 (9 x 9) slabs.