Grábrók is a small volcano in the north of Borgarfjörður area, about 45 kilometers north from Borgarnes town in the West part of Iceland. Grábrók is about 170 meters high mountain north of Bifröst village and Lake Hreðavatn. The volcano is about 3400 years old, and Grábrók is one of three craters in the area, one is called Grábrókarfell (Rauðabrók) and another is called Litla Grábrók (Smábrók). The lava that flowed from the volcano is about 7 km2 and its average thickness is about 20 meters, the lava type is AA lava.
The lava field from Grábrók is very different from other sights and landscape in the area. The lava flowed through Norðurárdalur valley and changed the riverbed, it is also believed that Lake Hreðavatn was formed when the lava blocked the valley there.
There is an easy walk up to Grábrók from the north side. It is a great place to rest after driving from Borgarnes and to enjoy the nature, it is one of the easiest place in Iceland to go to the top of a volcano.
Other interesting places in the area include the waterfall Glanni which is a beautiful waterfall where the Norðurá river falls through the cliffs. In the summer you can see the salmon jumping up the waterfall, while Norðurá is one of the most famous salmon fishing rivers in Iceland. It is nice to walk from Grábrók volcano along the river banks of Norðurá to Glanni waterfall and to Paradísarlaut.
From Reykjavík the drive is about 1 hour and 20 minutes to Grábrók. Take Ring Road nr. 1 towards Borgarnes town, keep going until the university of Bifröst. Turn where the sign says Hreðavatn.