The bizarre swirls, spirals, rosettes, honeycombs and basalt columns at Hljóðaklettar (Echo Rocks) are a highlight of any hike around Vesturdalur and a puzzling place for amateur geologists. It's difficult to imagine what sort of volcanic activity produced these twisted rock forms. Dazzling concertina formations and repeat patterns occur throughout, and the normally vertical basalt columns (formed by rapidly cooling lava) show up on the horizontal here.
These strange forms and patterns create an acoustic effect that makes it impossible to determine the direction of the roaring river, a curiosity that gave the area its name.
A circular walking trail (3km) from the parking area takes around an hour to explore. The best formations, which are also riddled with lava caves, are found along the river, northeast of the parking area.