Flisvos Park

Take the tram to this highly family-friendly park with loads of playground facilities and the summer Theatro Skion Tasou Konsta, plus an open-air cinema. The coast just east is also the closest beach to central Athens (get off the tram earlier at Mousson, for instance). It's small and a bit rocky, but it's edged with a promenade where locals take their evening volta (stroll). Overall, a nice escape from the center and chance for sea breezes.