Lake Wörthersee

Go swimming in the lake Wörthersee, right south of the city centre. The water is extremely clean and clear, and very warm in the middle of the summer. Note that pretty much the entire shore of the lake Wörthersee is private property, because of the dense population of Austria. This means that in practice, you have to be a guest of a lakeside hotel ("Seehotel" in German) to actually get to the lake shore, and even then you can only visit your own hotel's property. Your hotel will tell you where its share of the lake shore is, and provide you with a key if one is necessary. It is advised to bring your own swimming costume and towel. The lake itself is public property, so you can swim anywhere you like. Just note not to trespass on other private properties at the shore. When swimming far from the shore, watch out for speedboats, as these are common nearer the centre of the lake.