The name Forbidden City is derived from the rule that only the emperors and their court could enter the premises, with the exception of a select students who received the highest scores on a national exam (the "Emperor's Exam")and could enter the city for one day to share their knowledge with the emperor and his advisors. Not even the emperor himself could leave the city except on special occasions since the city was equipped to cover every need.
After the communist revolution, the emperor was expelled from the Forbidden City and the grounds became public property of the People's Republic of China. Knowing this historical transformation is important to understand the grandiosity of the Forbidden City. And when I say grandiosity, I mean it in every sense of the word.