Covering about eight square kilometers, Kleifarvatn is the largest lake on the Reykjanes peninsula and with a maximum depth of 90 meters is one of the deepest lakes in Iceland. Kleifarvatn is located about 30 km outside of Reykjavík and sits directly atop the mid-Atlantic ridge, the point at which the North American and Eurasian continental plates diverge. Kleifarvatn Lake is nestled within an impressive volcanic landscape, full of steep and amazingly colored hills and weird lava formations. Standing at the lake’s shore it is hard to believe that there is a populated city just 30 minutes away. This is the territory of trolls and elves. Lake Kleifarvatn’s position on the geothermally active area along the diverging tectonic plates provides some unusual features. Underwater hot springs were recently discovered about 10 meters from the shore on one side of the lake. In the center of the hot springs is a large crater that emits large quantities of warm water and gases. As the air bubbles are pushed through the crater on the lake floor, pressure causes the surrounding rocks to vibrate slightly. Divers can usually feel these vibrations themselves, which is a special experience! Kleifarvatn lake is also unusual because of its constantly rising and falling water levels despite the fact that the lake has no visible surface drainage, i.e. no connecting rivers. Changes in water level are due mostly to alterations in ground water level. For instance, the water level in the lake noticeably decreased in 2000 as water drained into the ground following earthquakes that created a fissure in the lake’s floor. Since then the water levels have risen again, but they must be checked frequently in order to gauge access to the dive site. Kleifarvatn Lake is a popular fishing site during the summer season and is known for unusually large brown trout and char. A monster the size of a whale and shape of a serpent is also said to inhabit the lake. As the lake partially freezes over during winter, both diving and fishing activities are paused during the winter season. The nearby Seltún geothermal area makes for an interesting stop, where you can observe the boiling mud pots, the colorful sulfur deposits and the intense geothermal activity that characterizes Iceland.