Grüner See (Green Lake) is a lake in Styria, Austria. During the winter, the lake is only 1–2 m deep and the surrounding area is used as a county park. However, during the spring, when the temperature rises and the snow melts, the basin of land below the Hochschwab mountains fills with water. The lake reaches its maximum depth of around 12 m from mid-May to June and is claimed to look the most beautiful at this time. Read more about it here.