The lake Weißer See in the district Weißensee seems to be one of the last oases in the concrete jungle of Berlin and is situated only 20 minutes by tram M4 from Alexanderplatz.
It looks like a park from the outside, but as soon as you enter the green forest you will find a circular lake, which seems totally isolated from the outside world. The whole bank offers nice little nooks and views to relax and swim, but the Strandbad (lido) on the eastern side offers some extras like a sandy beach, sun loungers, showers, a bar, snacks (like ice cream, yummy!) and BBQ.
The Strandbad is open daily when it’s not raining. When it’s swimming weather the entrance is € 5.50 (€ 3.50 reduced fee). If you only want to sit on the terrace without swimming, you can enter for free until 19:00. After 19:00 it costs € 1.
If you prefer walking you can take a stroll around the lake, let your kids romp on the playground or have a seat on a bench. Weißer See is just perfect for a Sunday no matter the weather.