Herthasee is a lake on the island Rügen, Mecklenburg-Vorpommern, Germany. At a length of 170 m and a width of 140 m, it covers a surface area of 0.202 km². It has a maximum depth of 11 m. It is located in the center of the Jasmund National Park and its famous chalk cliffs.
At its embankment, the lake features a Slavic hill fort called Herthaburg, with a height of 17 m. It was constructed and inhabited between the 8th and 12th century.(Wikipedia)