Liquidrom
Germans love their thermal baths and saunas, and this is one of the classiest around. The dramatic main thermal pool lies under a vaulted ceiling, where glowing lights and soothing music that can be heard underwater enhance a feeling of calm. In addition to several saunas and a steam room, take advantage of the outdoor hot tub in the enclosed courtyard, best at night under stars. There's a bar and a healthy snack menu, just in case all that relaxation leaves you hungry. Full nudity is to be expected here, even in coed areas.