The Roman Bathhouse developed through the Byzantines into the Muslim Hammam ... something every Classicist should experience (although I recommend skipping the African Mikvah experience).
In Marrakech I highly recommend LesBains de Marrakechwho do a slightly adapted version visitors prefer - and ask for the Shiatsu Master who is not listed, but does a massage unlike any shiatsu I've ever had and is simply amazing. (I have not tried their new French outpost but their standards are high, and I stayed there when they were first experimenting with a riad).
Bathing does not have to be simply hygiene - do like the Romans did and make it a cultural experience with a good book or music ... even a movie playing on a laptop.
Hygieia was a goddess for good reasons!