Zürich has a strong culture of swimming in the city waters. When the temperature climbs, casual beachwear replaces the usual chic on the streets and in the parks. There are plenty of opportunities to sunbathe in the city. The options range from comfortable child-friendly lakesides to women/men-only facilities and free grass in a park.
Oberer Letten is an exception. It is a free badi (swiss germ. for an open-air public bath) built on the river Limmat. All the facilities include changing rooms, showers, storage lockers, and sunshades. The difference to most places lies in the crowd, Oberer Letten is very popular amongst the younger population. Usually, in the evenings and over the weekends, it is filled with big friend groups, loudspeakers, exposing clothing, and alcohol. The area around the river has a chill vibe and underground aesthetics. Local terraces have a wide offering in case you forgot to bring your own snacks and drinks.
Off-season, the area around Oberer Letten makes a great walk from the train station and back. Many of the terraces in the area (for example Chuchi am Wasser or Stazione Paradiso) remain open all year round. On your way, you will also get a chance to observe some graffiti art and the views of the ex-industrial center of Zürich – the Hardbrücke area. For a complete overview, start at the main train station and follow the Neumühlequai and continue on the Kloster Fahr-Weg until the Kornhausbrücke. Coming back pass by Platspitz park.