The Blue Lagoon geothermal spa is one of the most visited attractions in Iceland.
The spa is located in a lava field in Grindavík on the Reykjanes Peninsula, southwestern Iceland.
It is about 13 km (8 miles) from the Keflavík International Airport and 39 km (24 miles) from the capital city of Reykjavík.
The Blue Lagoon spa and geothermal complex is clearly visible from any of the usual satellite imagery sources at coordinates (63.880, -22.449).
The warm waters are rich in minerals like silica and sulphur.
Bathing in the Blue Lagoon is reputed to help some people suffering from skin diseases such as psoriasis.
The water temperature in the bathing and swimming area of the lagoon averages 37–39 °C (98–102 °F).
The Blue Lagoon also operates a Research and Development facility to help find cures for other skin ailments using the mineral-rich water.
The lagoon is a man-made lagoon which is fed by the water output of the nearby geothermal power plant Svartsengi and is renewed every 2 days. Superheated water is vented from the ground near a lava flow and used to run turbines that generate electricity. After going through the turbines, the steam and hot water passes through a heat exchanger to provide heat for a municipal water heating system.
Then the water is fed into the lagoon for recreational and medicinal users to bathe in.
Reference: Wikipedia