The Baltoro Mustagh is a subrange of the Karakoram mountain range. It is located in Baltistan region, a northern political entity of Pakistan bordering Xinjiang Province in south-western China. The crest of the mountain range forms part of the Pakistan-China border and many of the summits of its highest peaks stand on the border itself. The Karakoram mountain range, of which the Baltoro Mustagh is just a part, contains the greatest concentration of the very highest mountains in the world - those above 7000 metres - and also the longest glaciers outside of the polar regions.
The range includes four summits over 8,000 metres, the most notable of which is K2. Rising to 8,611 metres (28,251 ft), K2 is the second highest mountain in the world. The other three 8,000 metre peaks are, Gasherbrum 1, 8,080 metres (26,509 ft), Broad Peak, 8,051 metres (26,414 ft), and Gasherbrum 2, 8,034 metres (26,362 ft).
The Baltoro Mustagh is bounded on the south by the Baltoro Glacier which gives rise to the Shigar River, a tributary of the Indus River. The Baltoro Glacier is 63km long and fed by several large tributary glaciers. These include the Godwin Austen Glacier flowing south from K2, the Abruzzi and the various Gasherbrum Glaciers flowing from the Gasherbrum group of peaks, the Vigne Glacier flowing from Chogolisa, and the Yermandendu Glacier flowing from Masherbrum. The confluence of the main Baltoro Glacier with the Godwin Austen Glacier is known as Concordia; this is the location of K2 base camp, a superb viewpoint for the major peaks in the area that has become a popular trekking destination.
The trough of the Baltoro glacier is very wide and the side walls are steep; the many side valley glaciers form icefalls where they meet the main glacier. Overlooking the northern boundary of the Baltoro Glacier are numerous spectacular rock towers and fine cliffs offering some of the most challenging rock climbing to be found anywhere in the world. The most notable of these are Trango Towers, Mustagh Tower, Cathedral Peak, Uli Biaho Peak and Paiju Peak.
The gateway to the Baltoro Glacier and its surrounding peaks leads from the town of Skardu through the Shigar Valley and Braldu Gorge. The valley stretches about 170 km from Skardu to Askole, the last permanent settlement but still far from the high mountains themselves. This route was difficult and dangerous due to frequent rockfall from the unstable valley sidewalls; river crossings were also only possible using rudimentary cable and box bridges. However the dirt road from Skardu was extended as far as Askole in 1988 and substantial and permanent bridges were installed along its route.