Thermalbad & Spa Zürich
Time Out says
The view over the city from Thermalbad & Spa Zurich's rooftop pool is amazing. You can also relax in the tubs in the basement and enjoy the Irish-Roman spa.
The view over the city from its rooftop pool is simply amazing, and that alone would almost be worth the entrance. But on top of that, you can also relax in the huge wooden tubs of the old brewery in the basement and - for an additional fee - enjoy the Irish-Roman spa with its steam baths and shallow pools. If you want to go on a Sunday, get there early, as there will be a queue before lunchtime.