Jardbödin or the Myvatn Nature Baths, is a little like the "Blue Lagoon" of the north of the country. It offers the same setting: swim in hot alkaline waters of a superb turquoise blue, in large lava pools. It is a superb outdoor area where your head keeps cool and your body is nice and warm!
I love the Jardbödin pool because it is relatively uncrowded, the entry ticket is affordable, the equipment is very good quality and it is ideal when you want to warm up and relax after a long day of walking.
When I am in Myvatn, I sometimes go there several nights in a row but at least once is a must.