Ancient Chinese astronomers believed that the purple star of Polaris, was in the center of Heaven, and that the Heavenly Emperor lived in the Purple Palace. The palace for the emperor on Earth was therefore, called the purple city. It was forbidden to enter the palace without special permission from the emperor. This is why the complex was called "the purple Forbidden City', which was shortened to 'The forbidden City".
The forbidden City is the World's largest palace complex and covers 74 hectares. It is surrounded by a 52 meters wide moat, and a 10 meter high wall. The wall has a gate on each side. The bricks for the wall were made from white lime and glutinous rice while the cement is made from glutinous rice and egg whites. These incredible materials make the wall extraordinary strong.
There are more than 8700 rooms in the complex, construction of the palace complex began in 1407, and moved from Nanjing to Beijing the next year.
Since yellow is the symbol of the royal family, it is the dominant color in it. Roofs are built with yellow glaze tiles and decorations in the palace are painted yellow.