Tourists visit Tongwancheng ruins in NW China

（Xinhua）  14:31, September 14, 2012

The Xiongnu was a northern nomadic ethnic group that was influential in northern China for 10 centuries in ancient times. The Tongwancheng walls are made with sand and white-powdered earth mixed with glutinous rice water. This mixture makes the earthen walls as hard as the stone walls. In 1996, the State Council designated Tongwancheng as the national key cultural relics protection unit. Now the local government is preparing to apply for world cultural heritage.