In the location's words:

The Stadtparksee natural pool is located in the middle of Hamburg's Stadtpark and is the perfect spot if you want to swim naturally and freshly in summer. The water is purified by natural filter systems without any chemicals - a real organic bathing experience in the city. Surrounded by green meadows and old trees, the pool not only offers refreshment, but also plenty of space for sunbathing and relaxing. There are shallow areas and a water slide for families, while swimmers can enjoy the large pool. A wonderful place to spend the summer relaxing and cooling off in the middle of Hamburg.