China's landscape is vast and diverse, ranging from the Gobi and Taklamakan Deserts in the arid north to the subtropical forests in the wetter south. The Himalaya, Karakoram, Pamir and Tian Shan mountain ranges separate China from much of South and Central Asia. The Yangtze and Yellow Rivers, the third- and sixth-longest in the world, respectively, run from the Tibetan Plateau to the densely populated eastern seaboard. China's coastline along the Pacific Ocean is  long and is bounded by the Bohai, Yellow, East China and South China seas. China connects through the Kazakh border to the Eurasian Steppe which has been an artery of communication between East and West since the Neolithic through the Steppe route – the ancestor of the terrestrial Silk Road(s).