The reason Bük exists in its current form. The Bükfürdő thermal complex is one of the largest spa resorts in Hungary, with twenty-seven pools spread across an indoor wellness building and a sprawling outdoor park. Water temperatures range from cool plunge pools to the 38 °C medicinal baths where Hungarian and Austrian pensioners sit shoulder-to-shoulder for hours.
Day tickets are good value by Central European standards, and the place is genuinely large enough that even busy summer days don't feel cramped. The medical centre runs musculoskeletal and rheumatological treatments for which Hungarian state health insurance partially pays — half the clientele in winter are there for medical, not recreational, reasons. Bring flip-flops and a towel; the gift shop sells both at a markup.