Grábrók is a crater formed by a fissure eruption approximately three thousand years ago. The fissure that initially opened during that eruption wasn't very long but left behind Grábrók and her two crater sisters that can be seen when on top. Also, from the top the massive lava about seven square kilometers that surfaced in that eruption is visible. It is a sight of geological interest comparable to Lakagígar, the Laki craters in the Icelandic Highland accessible from the Southern Region. The view from the top is not only interesting because of the lava. It is an impressive view over the most beautiful part of the Western Region Borgarfjörður and the tiny but beautiful lake Hreðarvatn, that was formed during that eruption. To the northwest is a view to Baula a cone shaped and colorful mountain.
The walk to the top is quite easy as the crater is only about 170 meters high (560 feet). There is a good path up to the top with manmade steps. It is one of the natural sights that are basically on the Ring Road in Iceland and has been popular among Icelanders for decades.