There are two options on M class. There is a dry sauna for free just inside the men's & women's bathrooms inside the spa area just off the indoor pool. Anyone can use them. although they are somewhat hidden away. They are nice becuse they have a huge viewing window out to the sea. For a fee--whihc varies per ship you can get passes to the Persian Garden area by the day or several days or the entire trip. Pass entitles you to use the Private steam rooms. Some are aromatherapy, some very hot..there are twinkilng lights & heated benches.There areneat showers with varying sprays & temps This is co-ed.. Have used them on both Connie & Summit. They are OK but because they are interior rooms they can feel enclosed, dark etc. Also on Summit--not everything worked the way it was supposed to & was not fixed. BY contrast the Private sauna/steam area on Brilliance (Royal) faces out to the sea, is really great & has heated loungers. Take your pick! None were ever crowded on any ship....also great as no children are allowed!