Amalienbad is a large public bath built between 1923 and 1926, with Art Deco interiors that make it more interesting than a routine swimming pool. The main hall, tiling, and period details are the draw even if you only come for a swim.
The pool can be busy, so it is better for a relaxed bath-house visit than serious lane swimming. Sauna areas cost extra and include warm and cold pools, steam rooms, and Finnish sauna sessions.