Sieglsee
Sieglsee is the name of two adjacent lakes in Tyrol, Austria, the Große Sieglsee and the Kleine Sieglsee.
They are nearly circular sinkhole lakes. The Große Sieglsee has a diameter of about and is about deep, the Kleine Sieglsee has a diameter of about. The lakes came into existence as collapse sinks in the Raibl Formation with sandstones, slate and rauhwacke. The lakes drain via the river Sieglseebach into the Schwarzwasserbach. The deep and clear lakes are used for diving.