Blue Lagoon is a Geot­her­mal Spa locat­ed in a lava field between Keflavik Inter­na­tion Air­port and Reyk­javik in south­west­ern Ice­land. The lagoon is a byprod­uct of the near­by geot­her­mal pow­er plant. 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 hot water pass­es through a heat exchang­er to pro­vide heat for a munic­i­pal hot water heat­ing sys­tem and is final­ly fed into the lagoon. The warm waters are rich in min­er­als and bathing in the Blue Lagoon is reput­ed to help many peo­ple suf­fer­ing from skin dis­eases. The water tem­per­a­ture in the bathing and swim­ming area of the lagoon aver­ages 40 °C (104 °F) and is enjoy­able year round, even in freez­ing con­di­tions.