At the southwest corner near where the Yellow River emerges from the Tibetan Plateau is Lanzhou, the westernmost large city in north China and the capital of Gansu. To the west of Lanzhou is Xining from whence caravans (and now the railway) started for Lhasa. North of Xining the Gansu or Hexi Corridor runs along the northern edge of the Tibetan Plateau. This corridor and the Wei River valley became the main silk road route from China proper to the Tarim basin and westward. Downriver (north) from Lanzhou is a gorge through Gaolan County and Baiyin. The river emerges from the mountains and enters Ningxia near Zhongwei. It runs east with the Tengger Desert in Inner Mongolia to the north and hills to the south. It turns north through dry country to past the Qingtongxia dam to the irrigated area around Wuzhong City. It continues north past Yinchuan, the capital of Ningxia. To the west are the Helan Mountains. The river leaves the northern tip of Ningxia south of Wuhai, flows through desert and enters a large irrigated area at Dengkou. At the northwest corner the Lang Shan mountains force the river to turn east near Linhe. Here there is an irrigated area between the mountains and river and desert to the southeast. Near the center of the northern stretch is the large town and irrigated area of Baotou. The main road south runs from Baotou to Xi'an. About 70 miles northeast of the northeast bend is Hohot, the capital of Inner Mongolia. The river turns south, enters the loess plateau and forms a gorge at least 200 feet below the surrounding hills. There are no large towns in this region. There is a dam apparently called Wanjia and another further south and then the Hukou Waterfall of the Yellow River, the second highest in China. The river leaves the gorge near Hancheng, receives the Fen River from the east and the Wei River from the west. At its juncture with the Wei the Yellow River turns east toward the North China Plain. One can go upstream on the Wei with the Qin Mountains with Mount Hua on the south past Weinan to Xi'an, a former capital of China and now a large city. West of Xi'an is Xianyang, the Qin dynasty capital. The river exits the mountains west of Baoji. There is a dam, the river narrows and becomes yellow and the railroad needs many bridges and tunnels all the way to Tianshui. Upstream various tributaries extend in the direction of Lanzhou.