Basalt Architects has used marine-grade concrete to build Guðlaug Baths, a geothermal pool on Langisandur Beach in Iceland. The baths consist of a three-tiered structure, with a viewing deck on the top, a warm geothermal pool in the middle, and a cold-water pool at the bottom.

Read more on Dezeen: https://www.dezeen.com/?p=1621561​