One view is that this is related to the ancient allusion of "purple gas coming from the East". Legend has it that Laozi went through the customs to Hangu Pass, and the purple gas was seen by the guards from east to east. Not long after, Lao Tzu came riding a green cow, and the breeder knew that this was a saint. The gatekeeper asked Lao Tzu to write the famous Tao Te Ching. Therefore, purple gas is considered auspicious, indicating the emergence of sages and treasures. Du Fu's poem "Autumn Prosperity" said: "Look at the Yaochi in the west, the Queen Mother will descend, and the purple gas will fill Dongguan." From then on, the ancients called the auspicious Qi Ziyun, the legendary immortal's residence as Hai Zi, the immortal as Ziquan and the suburban road as Mozi. Purple gas comes from the east, symbolizing auspiciousness. It can be seen that the "purple" of the Forbidden City is well-known. The place where the emperor lived was so heavily guarded that ordinary people could not enter it, so it was called the Forbidden City.
Another view is that the origin of the Forbidden City is related to superstitions and legends. The emperor pretended to be the son of the emperor of heaven, that is, the son of heaven. Tiangong is the place where the Emperor of Heaven lives, and naturally it is the place where the Emperor of Heaven lives. "Guang Ya Shi Tian" says: "The name of the Heavenly Palace is Purple Palace." Therefore, the palace where the emperor lived was called the Purple Palace. There is also a saying that the origin of the Forbidden City is related to the ancient theory of "imperial wall". Ancient astronomers divided the stars in the sky into three-walled and twenty-eight star constellations. Three walls refer to Qiu wall, Shi Tian wall and Wei Zixing wall. Wei Zixing Yuan, known as the Emperor, is located in the center of Sanyuan. Purple MSI is the Big Dipper, surrounded by stars. In ancient times, there was a saying that "purple is above the middle" and "Emperor Taiping sat in the middle, and Qing officials were divided into four seas".
Because the ancients compared the Emperor of Heaven to the Purple Star Garden, which became the land of emperors, the Forbidden City was also called Purple Pole, Purple Forbidden City and Purple Garden. The saying of "purple ban" existed as early as the Tang Dynasty. The Forbidden City in Beijing covers an area of 1.087 mu, with a length of 96 1 m from north to south, a width of 753 meters from east to west and a circumference of about 7 li. There are more than 9,000 temples, and the surrounding walls are 10 meters high. It is not only worthy of the name, but also contains the meaning of the city of emperors.
Throughout the buildings in the Forbidden City, the Hall of Supreme Harmony, which symbolizes the sublimity and greatness of "Heaven", is located in the center of the Forbidden City and is the highest and most prominent place. It symbolizes the close connection between heaven and earth, Kunning Second Palace. On both sides of them, there are two doors, the sun mirror and the moonlight, which symbolize the sun and the moon. The array building outside the sixth house symbolizes twelve stars and represents the stars in the sky. This is a symbolic building complex.
The old name of the Forbidden City, the Forbidden City, can be said to be highly unified and perfect in naming and architectural design from the perspective of "Xing Yuan".