2 km south of Hraunsnef you find the 3000 year old volcano Grábrók. Grábrók is the biggest crater of three along a short volcanic crack. There are very good walking paths up to the crater. On the top you have a magnificent scenery over Borgarfjordur to the south.
The waterfall Glanni is about 5 km south of Hraunsnef in the river Norðurá. The river Norðurá is one of the best salmon rivers in Iceland. In the waterfall you can see a man made stair for the salmon to jump up the waterfall. A convenient walking path leads to Glanni, surrounded by beautiful landscape. Paradísarlaut - the Hollow of Paradise - is a beautiful oasis in the lava on the banks of Norðurá, not far below the waterfall Glanni. An easy walking paths leads to the hollow.
The lake Hreðavatn is just across the cross the road form Glanni, you take the road by Bifröst Universety
A possibility to do some trout fishing. If you want to go fishing you need to by a permit see here
Deildartunguhver is Europe's most powerful hot spring. It provides at the moment 200 l/sec of 100°C hot water.
Most of the water used for central heating in the towns of Borgarnes and Akranes is taken from Deildartunguhver. The hot water pipeline to Akranes is 64 km long, the longest in Iceland and the water is about 78 - 80 degrees when it reaches Akranes.
Look for the bright green "skollakampi" or hard fern (Blechnum spicant), quite common in other countries, but found only in this area of Iceland, thanks to the permanent warmth and humidity.
Hraunfossar are one of nature’s most beautiful gifts in Iceland. The Hraunfossar are hundreds of meters wide and are crossed by a bridge on one side. Further along, there is another waterfall called Barnafoss (Children´s waterfall). The waterfall Barnafoss is in River Skjalfandafljot near the abandoned farm Barnafell in Ljosavatn County. There the river runs in a narrow, and close to 100 m deep canyon. According to legends, young and brave men jumped across its narrowest parts. During prolonged subzero periods, the spray creates an ice arch across the river above the waterfall and sometimes a rope was strung across the river there to quicken this development. Flocks of sheep were driven over that bridge to graze on the Thingey Island between the two branches of the river.