<P> The history of the Forbidden City begins in the 15th century when it was built as the palace of the Ming emperors of China . It is located in the centre of Beijing, China, and was the Chinese imperial palace from the mid-Ming Dynasty to the end of the Qing Dynasty in 1912 . It has been a museum since the 1920s . </P> <P> Built from 1406 to 1420, the palace complex has undergone many changes . After serving as the imperial palace for some five hundred years, the Forbidden City became a museum, the Palace Museum, in 1925 . In 1987, it was declared a World Heritage Site by UNESCO . </P> <P> The site of the Forbidden City was situated on the Imperial city during the Mongol Yuan Dynasty . After the collapse of the Yuan Dynasty, the Hongwu Emperor of the Ming Dynasty moved the capital from Beijing in the north to Nanjing in the south, and in 1369 ordered that the Yuan palaces be razed . His son Zhu Di was created Prince of Yan with his seat in Beijing . In 1402, Zhu Di usurped the throne and became the Yongle Emperor . He made Beijing a secondary capital of the Ming empire, and construction began in 1406 of what would become the Forbidden City . The Forbidden City's plan was designed by many architects and designers, and then it was examined by the Emperor's Ministry of Work . The chief architects and engineers include Cai Xin, Nguyen An, a Vietnamese eunuch, Kuai Xiang, Lu Xiang and others . </P>

When did the forbidden city became a museum