The eastern half of the province is a limestone plateau with karst scenery and unnavigable rivers flowing through deep mountain gorges; the western half is characterised by mountain ranges and rivers running north and south. These include the Nujiang (Thai: Salween) and the Lancangjiang (Thai: Mekong). The rugged, vertical terrain produces a wide range of flora and fauna, and the province has been called a natural zoological and botanical garden.