Stock Photo - Landmannalaugar. Brennisteinsalda bathing place near Landmannalugar Camping is one of the most popular treasures in Fjallabak's nature reserve. This natural hot spring is located right at the edge of a 500-year-old hardened lava field called Laugarhaun and in the middle of the Torfajökull caldera, a large circular crater that extends over 15 kilometers in diameter. The name "" Brennisteinsalda "" means "" Sulfur wave "" and echoes the region's natural scent. While the heat is comfortable, expect small currents to cause rapid rises and falls to the water temperature. This moderate bathing area is located at the intersection of a cold water stream and a geothermal runoff above 38 degrees Celsius (100 degrees Fahrenheit). This combination allows you to move in the water and find the perfect mix of hot and cold. Natural convection even forms a noticeable difference between the cold water at the bottom of the pool and the hot water at the surface. There is room for over a dozen people to enjoy the water at once, although some may have a hard time resisting the small waterfall that flows over the cliffs at one end of the pool.