We just disembarked the europa, used the thermal area 3 times in our week.
Two days were port days and it was quiet and last visit was on sea day and it was much busier.
Plenty in there to do and very clean.
Steam room, pool area with vertical water coming down which massages your back, two saunas both with windows overlooking the ocean, ice bucket with chain to pull to release old water over you, Ice room (real snow inside to run over your body), showers with jets, hot and cold foot pools (6) and a mediterrean room (bit like steam room but less steam) and 2 rooms with 4 heated beds in.
Well worth a visit, hope this helps.
If you visit the spa when you board they will show you found the areas before you commit too.