Cutting into the northeast’s rocky inland plains some 60km east of Húsavík, Jökulsárgljúfur National Park – an isolated fragment of the enormous Vatnajökull National Park – encloses a 35km stretch of the Jökulsá á Fjöllum, Iceland’s second-longest river. Originating almost 200km south at Vatnajökull, for much of its journey through the park the river flows through the mighty Jökulsárgljúfur, a canyon which is 120m deep and 500m wide in places, forming several exceptional waterfalls and an endless array of rock formations. There are two key sights: the horseshoe-shaped Ásbyrgi canyon in the north of the park; and Dettifoss, Europe’s most powerful waterfall, at the park’s southern boundary. In between, the silt-laden river cuts its way between stark grey gorge walls, all set against an unusually fertile backdrop: over half of the country’s native plant species are found here, and in summer the heathland above the gorge is lush and splashed pink and white with flowers – except in a couple of places, however, trees are rare.
With three or four days to spare, the park can be thoroughly explored on foot along marked hiking tracks, the longest of which follows the west side of the gorge for 35km between Ásbyrgi and Dettifoss. Two roads also run south for about 60km through the park to Dettifoss and the Ringroad east of Mývatn: Route 862 follows the west side of the gorge from Ásbyrgi, and is rough gravel except for the excellent final 20km stretch between Dettifoss and the Ringroad (there’s talk of surfacing this entire road by 2014); while Route 864 down the east side of the gorge is gravel the whole way. Both roads are closed through winter.