This is completely in nature but SUPER COOL. Located about 45 minutes from Reykjavik, this hike is 1 hour each way. The way there is completely uphill but the views are rewarding. You'll be walking along a geothermal river the entire time, but it is most warm at the top. Once you reach the swimming area, where it is as hot as a hot tub, there are changing nooks but no real facilities. This is completely in nature but SUPER COOL. Where else can you swim in a hot river?