Baltistan is a rocky wilderness of around , with the largest cluster of mountains in the world and the biggest glaciers outside the polar regions. The Himalayas advance into this region from India, Tibet and Nepal, and north of them are the Karakoram range. Both ranges run northwest, separated by the Indus River. Along the Indus and its tributaries are many valleys. Glaciers include Baltoro Glacier, Biafo Glacier, Siachen Glacier, Trango Glacier and Godwin-Austen Glacier.