The Biafo Glacier is a 63 km (39 mi) long glacier in the Karakoram Mountains of Gilgit Baltistan, Pakistan which meets the 49 km (30 mi) long Hispar Glacier at an altitude of 5,128 m (16,824 ft) at Hispar La (Pass) to create the world's longest glacial system outside the polar regions. This highway of ice connects two ancient mountain kingdoms, Nagar (immediately south of Hunza) in the west with Baltistan in the east. The traverse uses 51 of the Biafo Glacier's 63 km and all of the Hispar Glacier to form a 100 km (62 mi) glacial route.
The Biafo Glacier presents a trekker with several days of very strenuous, often hectic boulder hopping, with spectacular views throughout and Snow Lake near the high point. Snow Lake, consisting of parts of the upper Biafo Glacier and its tributary glacier Sim Gang, is one of the world's largest basins of snow or ice in the world outside of the polar regions, up to 1,600 m (0.99 mi) in depth.
The Biafo Glacier is the world's third longest glacier outside of the polar regions, second only to the 70 km (43 mi) Siachen Glacier disputed between Pakistan and India and Tajikistan's 77 km (48 mi) long Fedchenko Glacier. Evidence of wildlife can be seen throughout the trek. The Ibex and the Markhor Mountain Goat can be found and the area is famous for brown bears and snow leopards, although sightings are rare.