Nanxi River, a tree-shaped water system with 145 kilometers in length, is the biggest northern branch in the row reaches of Ou River. It flows between Yandang Mountain in the east and Guochang Mountain in the west, both of which have trend of being high in the south and low in the north. The rock stratum of the mountains is mostly made up of tuff, rhyolite, and granit. The river lies in subtropical monsoon zone, while influenced by the maritime climate. It enjoys a warm and moisty climate all the year round and its temperature varies from 4.2 degrees centigrade to 38.2 degrees centigrade, with the average temperature of 18.2 degrees centigrade in a year. In the seenie spots, there are various kinds of plants and some rare trees (such as, Chinese sweet gum, and ginkgo). With charming scernery and simple local custom, Nanxi River was named as the National Tourist Scenic Spot by the State Council in 1988.