Plain Blue Banner, alternatively Zhenglan Banner in Chinese or Xulun Hoh Banner in Mongolian, is a banner of Inner Mongolia, China, bordering Hebei province to the south. It is under the administration of Xilin Gol League. Xanadu or Yuan Shangdu, one of the capitals of the Yuan dynasty, was located here. Today the ruins of Yuan Shangdu are listed as UNESCO world heritage site and are open to the public.