Helenesee is a lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 in Brandenburg

Brandenburg

Brandenburg is one of the sixteen federal-states of Germany. It lies in the east of the country and is one of the new federal states that were re-created in 1990 upon the reunification of the former West Germany and East Germany. The capital is Potsdam...

, Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

. Its surface area is ca. 250 ha. With a depth of 56.63 m, the Helenseee is the second deepest lake in Brandenburg, only surpassed by the lake Großer Stechlinsee

Großer Stechlinsee

Großer Stechlinsee or Lake Stechlin is a lake in Landkreis Oberhavel, Brandenburg, Germany. At an elevation of 60 m, its surface area is 4.52 km². The Stechlin cisco, a dwarfed fish, is found only in this lake...

. It is situated approximately 8 kilometers in the south of Frankfurt (Oder). It was formed after the flooding of a former open-pit mining

Open-pit mining

Open-pit mining or opencast mining refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow....

which started in 1958.