You are over 15 years old so get 50% off with your youth card
Located in the heart of the capital, the Badanstalt Aquatic Relaxation Center includes a swimming pool with whirlpools and water jet, two sauna cabins, a Turkish bath and solarium, rest areas, a fitness room as well as shower baths and tubs.
http://www.visitluxembourg.com/de/ansicht/pool/centre-de-relaxation-aquatique-badanstalt