One of the most romantic geothermal pools in Iceland is located inside the Grjótagja Cave. Now it is famous thanks to the Game of Thrones series. Due to recent changes in subsoil, there has been a change in water temperature and it has raised from 40°C to 50°C, too much for taking a bath (which is forbidden anyway). You can enter the cave through two openings. The cave and the geothermal pool are quite easily accessible in contrast to Stóragjá nearby.
How to find the geothermal pool in Grjótagjá Cave:
Photos of the geothermal pool in Grjótagjá Cave:
The Nearest Natural Geothermal pools