An island in the city: beyond the lake and the river, Zurich offers this attraction too. It just feels different to be surrounded by water from every side (trust me, I am Greek). Ok, the island in question is reachable through pedestrian bridges.
The Werdinsel is located in the river Limmat in the city quarter called Höngg and appeals to different people and tastes. The island is, naturally, most popular in the summer.
The upper (eastern) side offers supervised river bathing for the mainstream. Families would appreciate the natural shade of the trees (if desired) and the little pool and playground for the offspring.
The lower side is a popular nudist area (officially illegal since 1983) that is divided into two parts: the major part is primarily gay. The smallest part, separated from the rest by a shallow water canal, attracts a more mixed public. On both parts you may run across some quite creative body art. The gay part attracts also a lot of (dressed) barbecue visitors of all ages.
There is a summer festival (Inselfäscht) in July or August.
But the island is also ideal for walking, jogging and cycling during other seasons, especially during the autumn. The crowds are away and visitors can enjoy the exhilarating melancholy of the fallen leaves: ideal for a conversation or just self-reflection.
I have also heard of senior citizens bathing in the ice-cold river water during the winter (brrrr).