The Khunjerab Pass sits at 4,693 metres — the highest paved international border crossing in the world and the point where the Karakoram Highway crosses from China into Pakistan. The scenery around the pass is extraordinary: jagged peaks, glaciers, and high plateau grassland where yaks and Marco Polo sheep graze.
If you're travelling by public transport between Kashgar and Pakistan, expect to spend a night in Tashkurghan. Buses stop there and don't continue until morning — which is no hardship, as the old mud-brick fort is worth a look. The pass itself is the highlight of the KKH, not a destination in its own right.
Be aware that the pass closes to all vehicles except trucks during the rainy season (roughly December to April) due to mudslide risk. A Pakistani visa must be arranged in advance; Kashgar, Beijing, and Hong Kong are reliable places to get one.