The Mývatn Nature Baths are without a doubt one of my favourite pools in all of Iceland and not as touristy or crowded as the Blue Lagoon tends to be. They consist of a large lagoon, which has a temperature of about 36 to 40 degrees Celsius (97 to 104 degrees Fahrenheit), as well as several hot tubs and steamrooms.
Nearby places: Höfði, Vindbelgingur, Hverarönd, Skútustaðagígar
The water here is packed with minerals, particularly sulphur, which is said to be good for respiratory and skin problems.
The view from the main lagoon is also quite amazing, overlooking lake Mývatn with it´s endless islands and pseudo craters and surrounding lava fields and volcanoes.