The Hunza Valley is reached via the legendary Karakoram Highway, the road that links Pakistan to China through some of the most dramatic mountain country on earth. From Islamabad it is a long but spectacular drive — roughly 600 kilometres, two days on the road if you stop in Besham or Chilas overnight. Public buses (NATCO and private operators) run daily from Rawalpindi to Gilgit and on to Karimabad, but conditions vary with the season and landslides are common in the wet months.
The fastest way in is to fly. PIA operates flights between Islamabad and Gilgit when the weather cooperates — the route winds between Nanga Parbat and the Karakoram peaks and is one of the most scenic short-haul flights in the world. From Gilgit, it is a two- to three-hour drive up the highway to Karimabad. Flights are weather-dependent and frequently cancelled, so allow a buffer.
Coming from China, the Khunjerab Pass (4,733 m) opens roughly May to October. Buses cross the border at Sost on the Pakistani side. This is one of the great overland journeys, but be prepared for cold, paperwork, and the occasional closure.