Here’s a great article from the BBC – re Great Public Swimming Pools from around the world.
https://www.bbc.com/culture/article/20220729-the-best-public-swimming-pools-around-the-world
Highlights:
Iceland – both near Reykjavik: Blue Lagoon and Guðlaug Baths
United Kingdom
Birmingham: Moseley Road Baths
Penzance, Cornwall: Jubilee Pool
Austin, Texas: Barton Springs Pool
And here is another link for the 15 best pools: https://www.vacationsmadeeasy.com/TheBLT/The15MostAmazingPublicPoolsWorthDivingInto.html