Distance: approximately 7.5 km (one way). Route: Brúnastaðir in the Fljót area – the mouth of the Héðinsfjarðardalur valley – Grænuvallahnjúkur mountain.
Maximum elevation: 905 metres. Hiking time: 7-8 hours (both ways).

Grænuvallahnjúkur mountain is one of very few mountains north of the Lágheiði heath higher than 900 metres. From its summit, you have one of the best view – if not the best view – over the whole of Héðinsfjörður fjord, which opens up before you like an unfolded map below the mountain. To begin with, the trail in Héðinsfjarðardalur is followed up the gravel plains and brush covered slopes. In the mouth of Héðinsfjarðardalur valley, you turn off from that trail and the course is set up the gravel plains and from there onto the shoulder of the mountain, which is located between the Ólafsfjarðardalur valley and Héðinsfjarðardalur valley. This will be the steepest uphill climb on the route, there is some loose scree but it is easy to bypass the cliffs. The easier thing to do would be to hike up along a narrow shoulder, because there a good view opens up into the Ólafsfjarðardalur valley and over the Ólafsfjarðarskarð pass. When you have reached the shoulder, the ground there is stony and uneven and the remaining part of the hike is an over two-kilometre hike to the top of the mountain. During the hike, the view opens up little by little to Héðinsfjörður and over the mountains on both sides of the fjord. The view is good down to the Botnaleið route between Ólafsfjörður and Siglufjörður, where the route lies at the bottom of Héðinsfjörður fjord. A short distance east of Grænuvallahnjúkur is the Sandskarð pass and further to the east you can see the Ólafsfjarðarskarð pass. On the return journey, we take the same route as all other routes are hardly passable and long stretches are impassable.