Stuðlagil is a striking basalt-column canyon in the Jökuldalur valley of East Iceland, around 70 km from Egilsstaðir. Towering hexagonal columns line both sides of the gorge and frame the milky blue-green glacial water of the Jökla river — one of the largest concentrations of basalt columns in the country.
The canyon lay largely hidden underwater until the Kárahnjúkar hydroelectric plant reduced the river's flow, gradually revealing the formations and turning Stuðlagil into one of East Iceland's most photographed natural sights. You can view it from a platform on the west bank or hike to the east bank for a closer look; after heavy rain the water can turn brown with silt and conditions can change quickly.