Grundlsee, Lake in Styria, Austria.

Grundlsee is a 5.8 km long, 917 m wide lake at 708 m in the Styrian Salzkammergut, with an area of 4.22 km² and a maximum depth of 62 m. It lies in a steep basin at the southern foot of the Totes Gebirge, bordered by forested slopes; the settlement of Grundlsee sits on the northwest shore and Gößl on the east. The Grundlseer Traun drains it in the west.

The nearby Salzofen cave holds archaeological finds pointing to human settlement dating back 34,000 years in this region. Bronze Age and Iron Age artifacts from this site show how long people have inhabited these valleys.

The lake is marked by traditional wooden boats called Plätte, which local fishermen have used for generations as part of daily life here. These boats remain a defining feature of how people relate to the water.

Several designated beach areas around the lake offer stone, sand, and grass sections for swimming, with children's playgrounds nearby at different access points. Different shoreline sections suit various preferences, whether you want to wade in shallow areas or find rocky spots.

Water temperatures reach around 24 degrees Celsius during summer months, which is surprisingly warm for a mountain lake at this elevation. This mild temperature makes swimming comfortable even at high altitude.