Ásbyrgi

A horseshoe-shaped canyon 3.5 km long and 1 km wide, with 100-metre cliff walls on both sides and a birch forest on the canyon floor. Legend says it's the hoofprint of Odin's eight-legged horse Sleipnir; geologists say it was carved by catastrophic glacial floods. Either way, the scale is impressive and the forest feels completely out of place in the otherwise barren northeast.

The best walk is from the car park at the southern end to the rock island (Eyjan) in the centre of the canyon — about 30 minutes each way, flat and easy. The cliff-top viewpoint at the northern end gives you the full horseshoe perspective. Bring binoculars for nesting fulmar on the cliff faces.

Ásbyrgi is in the northern part of Vatnajökull National Park, about 65 km from Húsavík and part of the Diamond Circle route. It's one of the less visited major sites in the northeast — you'll often have the trails to yourself. There's a good campsite at the canyon entrance. Budget 1-2 hours for a proper visit.