The earliest foundation of Beijing was Youzhou City in the Tang Dynasty  in the following thousand years, Beijing had four large-scale development, or expansion, or new construction, namely, the capital of the Yuan Dynasty and the capital of the Yuan Dynasty  the inner city built in the early Ming Dynasty and the outer city built after the middle of the Ming Dynasty, the convex wall of Beijing was completed in this way
The Qing Dynasty inherited Beijing of the Ming Dynasty, leaving the overall layout system unchanged until modern times
The convex wall of Beijing was formed in the Ming Dynasty