Liepnitzsee with its crystal-clear water has long ceased to be an insiders' tip, yet it is still quite picturesque.
Crystal clear and refreshing water and everything else a lake can offer: Hike around the lake in one day, visit the island via ferry and have a snack at the island’s own rustic beergarden (our suggestion: potatoe salad). Or rent a boat or have a swim in the official swimming place: There you get everything you need for a nice day outside the city.