The lake is 32 metres deep, a basin which has been shaped by glaciers since the ice age. The water in the cool, oxygen-rich corrie lake comes from streams on the eastern side of the Seebuck. The seabed is loosely covered with water plants such as the rare quillwort.
The lake’s rock face rises above it out of the forest. The sunny, open spots amidst the rocks are home to many alpine plants.
An untouched, protected forest surrounds Lake Feldsee to the east and the north. The Feldsee is a nature preservation paradise, not a bathing lake. The protected quillwort plant grows near its shores.