A big sauna with a huge window looking out on the forest and the outdoor hot tub that's big enough for many people to warm up from the cold. This could also be used as a cold pool for dunking after sweating in the sauna.
Sunroom almost exactly. either this floor or repeat entryway floor. All metal windows and doors throughout, simple ceiling, chandelier, fireplace punches through from living room. (some thick metal areas around window/door frames)