Blue Lagoon Geothermal Spa.

Set in a stark black lava field on the Reykjanes Peninsula, the Blue Lagoon is Iceland’s most famous geothermal retreat. This man-made spa fed by the nearby Svartsengi power station is renowned for its mineral-rich, milky-blue water, which hovers at a comfortable 37–40°C. The striking color comes from a high concentration of silica, which guests slather on their faces as a natural mud mask, alongside algae and mineral salts. While it functions as a highly organized resort—complete with a swim-up bar, steam caves, sauna, and the lava-walled LAVA Restaurant—the core appeal remains the sensory contrast of soaking in steaming, opaque waters while exposed to the crisp Icelandic air. Located close to Keflavík Airport, it is a convenient, otherworldly introduction to the country's volcanic geology.