Tianjin is located at the lower reaches of the Haihe River, its territory lying on both sides of the river. Besides Haihe, several other rivers also run into the sea through the area, such as the New Ziya River, the Duliujian River, the New Yongding River, the New Chaobai River and Canal Ji. The distance from the city proper to the sea coast is 50 km and that to Beijing is 120 km. It is an important passage by sea to Beijing, having served as an important fort and doorway to Beijing since ancient times. It is also a communication hub linking north China, northeast China and northwest China. The direct distance from Tianjin to Shenyang in northeast China, to Baotou in northwest China and to Xuzhou and Zhengzhou in the south is less than 600 km. The city boasts the largest man-made harbor in the north; its Tianjin Port is an important passage linking a dozen of provinces and cities in the north with the sea. With more than 30 navigation routes leading to more than 300 international ports, it serves as a major channel linking the continents of Asia and Europe by sea. Tianjin's geographical position and strategic importance is unmatchable.