Correct! The Blue Lagoon is unnatural in the sense that it’s not a natural pool. It’s a by-product of the power plant next to the lagoon. If you come by a tour bus and enter from the main entrance you might never see the power plant itself, but if you explore the paths outside the lagoon, or keep an eye out from the road, you will definitely see it.
The power plant pumps heated water from the underground to run a turbine generating electricity. The water is then distributed through a heating exchange system to help provide heated water to the local municipality. Finally, some of the excess water is used to create the pool we know as the Blue Lagoon.
The pool water is around 37-39 degrees and changed every second day. It’s full of natural minerals claimed to have a healing effect.