Most of the large lakes of Upper Austria are in the south (Salzkammergut): Almsee, Attersee, die Gosauseen, Hallstätter See, Irrsee, Langbathseen, Mondsee, Offensee, Traunsee and Wolfgangsee. In the Oberinnviertler Seenplatte on the border with Salzburg, there are small lakes which are very warm in summer: Holzöstersee, Höllerer See, and Ibmer See.