In the north, the Hengduan Mountains form the border with China. Hkakabo Razi, located in Kachin State, at an elevation of , is the highest point in Myanmar. Many mountain ranges, such as the Rakhine Yoma, the Bago Yoma, the Shan Hills and the Tenasserim Hills exist within Myanmar, all of which run north-to-south from the Himalayas. The mountain chains divide Myanmar's three river systems, which are the Irrawaddy, Salween (Thanlwin), and the Sittaung rivers. The Irrawaddy River, Myanmar's longest river at nearly , flows into the Gulf of Martaban. Fertile plains exist in the valleys between the mountain chains. The majority of Myanmar's population lives in the Irrawaddy valley, which is situated between the Rakhine Yoma and the Shan Plateau.