There is one in Reykholt, in Flúðir and as well in Minni Borg. If you want to try out a natural hot spring swimming pool you should try Secret Lagoon or Fontana.
Secret Lagoon natural hot springs are located in the small village called Fludir and are in the Golden Circle area. It is natural and unique for guests so they can get the true Icelandic feeling. The pool’s natural surroundings and steam rising into the air gives the place a magical feeling. The warm water stays at 38-40 Celsius all year. In the whole area there are several geothermal spots and a little Geysir which erupts every 5 minutes, showing off for the guests relaxing in the hot spring. During winter, the northern lights often give a great lightshow above Secret Lagoon. What better way to view the spectacular light show overhead than relaxing in the pool’s warm water?
Fontana in Laugavatn are geothermal baths.A unique experience of the healing powers of the geothermal springs. Soak in a natural pool, listen to the bubbling hot spring in the steam rooms, or for the venturesome, take a dip in the refreshing lake. Since 1929, locals have been enjoying the healing powers of the natural steam baths by Lake Laugarvatn. Hot, healing steam simmers directly from the ground through grids in the cabin floors of the three traditional steam rooms. The temperature of the steam varies depending on the temperature of the hot spring and weather, usually between 40°C (104°F) and 50°C (122°F). Humidity is very high in the steam room cabins. Grids in the floor of the steam rooms allow guests to hear and smell the boiling natural hot spring right underneath, creating a natural and unique experience.