The Hengill area is in the middle of Iceland´s western volcanic belt, which stretches from the Reykjanes Peninsula to the Langjökull Glacier. Therefor there is a lot of geothermal activity on the area and many Hot springs in Nesjavellir.
It is really important that if you wish to visit a Hot spring do not start hiking without a tour guide or at least without consulting with the reception at the hotel first.
As written in the hiking chapter there is also a Hot spring in Reykjadalur near Hveragerði. There are several hiking trails and roads that lead to Reykjadalur. One is from Hellisheiði Power Plant and over the mountain (should not be walked without directions) and the other one is through the town of Hveragerði and up the hills and is very well marked so nobody can miss it.
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