Grundlsee, Lake, Styria, alt. 708 m, 5.7 km long, 0.9 km wide, 64 m deep; alpine lake nort-east of Bad Aussee in the Styrian part of the Salzkammergut region. It is the largest lake in Styria and is fed by the streams that drain the Toplitzsee (Toplitzbach stream) and Kammersee lakes. Due to the depth of the Grundlsee, water temperature is comparatively low; on the shores of the lake, municipalities of Goessl (alt. 720 m, summer holiday resort), Wienern (alt. 763 m) and Grundlsee (alt. 732 m, climatic health resort).