Khunjerab Pass, at 4,693 metres, is the highest paved international border crossing in the world, and it sits on the roof between Pakistan and China. The road climbs from Sost in a long series of gentle switchbacks, the tarmac smooth and wide, and the valley opens into a bleak, beautiful world of rounded brown mountains, snow patches and a sky that looks very close. A white gate marks the border and a modest stone sign says what you need to know.
The name means roughly valley of blood or the place where the stream flows, depending on who is translating, and the pass has been used by caravans for thousands of years. Marco Polo sheep, with their huge curving horns, live in the national park that surrounds the road, and with patience you may see ibex, marmots and, rarely, a snow leopard. Yaks graze in summer.
Be realistic about the ride. Oxygen is thin, so the bike runs rich and you feel it too: slow down, breathe, and take breaks. Weather can swing from sunshine to sleet inside an hour. The pass is open only in the warmer part of the year, generally from spring until late autumn, and it closes for snow, so check dates. Do not expect services on the pass itself beyond a seasonal tea stall.
The highway here is a monument to hard labour. Pakistani and Chinese work crews built it through some of the worst terrain on earth, and a memorial to the Chinese workers who died stands in Gilgit. Standing at the gate, with the road continuing north into Xinjiang, you can feel the line of history running through the stones.
Wear a warm jacket, even in July. The wind is bitter, and the cold sets in fast when cloud covers the sun. A short stay is the sensible plan, so take a photograph at the sign, enjoy the silence, and then roll back downhill toward the green of Hunza, where air feels rich and warm.