Kleifarvatn

Kleifarvatn is a deep, dark lake sitting in a volcanic fissure on the Reykjanes Peninsula, just 25 km south of Reykjavík. With a surface area of around 9 km² and a maximum depth of 97 m, it is the deepest lake in the region and has an eerie, almost otherworldly quality — its shoreline is bare black lava, and the water is an unusually deep blue-green.

The lake is notable for having no surface outlet river; water drains through fissures in the lake bed, and following the 2000 South Iceland earthquakes the water level dropped noticeably as new cracks opened. Hot springs and mud pools have been observed in parts of the lake floor. The area around the shore is also one of the most accessible sections of the Krýsuvík geothermal field.

A gravel road loops the lake and is suitable for most vehicles in summer. The lake is popular for fishing (arctic char) and hiking, and lies within easy reach of Reykjavík as a half-day excursion.