Solebad Bad Cannstatt draws on the mineral-water tradition that made this part of Stuttgart a spa district long before the city became shorthand for cars and engineering. The brine pools and wellness facilities are practical rather than grand, but they connect visitors with a real local habit of bathing in mineral water.
It is a good rainy-day or recovery stop, especially after a run of museums, hills, and city walking. Check opening hours, towel rules, and sauna etiquette before going; German bath complexes are straightforward once you know the routine, but they are not all arranged for casual tourism.