Beijing is the capital city of China, in downtown Beijing has a strong exterior surrounding city known as theForbidden City.Here was the emperor residence. It was built in 1406 and completed in 1420. In the past, it was used as the imperial residence for 24 emperors from Ming and Qing Dynasties. there is city moat about 50metres wild ,4 parts city wall corner towers ,Night and day he shielded by royal family and the royal family members. This huge city to extend a few kilometres.why was called