For hot summer days the Viennese are lucky that the city was built around the famous Danube. Thank you romans! There are a lot of places where you can cool yourself down in the river, but the most common is the “Donauinsel”. It is a huge artificial island that was built in the 1970ies and 80ies. There is a lot of public green to relax, as well as some sport facilities like volleyball courts and a skate park. If you favor skinny dipping, there are also quite big areas for that. Just look for signs that say “FKK”.
Every June there is the “Donauinselfest”. That is a 3 day music festival with 3 Million visitors which makes it the biggest worldwide! And the best thing: it is for FREE! Put on your party gear and hurry to “Donauinselfest”😎🎉.