No fee to use the normal exercise equipment. It's in the back of the spa (overlooking the bridge). I personally only used the treadmills, but there were nautilus type weight machines there too, as well as other aerobics machines like steppers, etc. There are also exercise classes periodically including a yoga on the adult beach at Castaway Cay. I'm pretty sure there's no charge for that.
Now as to the steamroom, I think that there would be a charge. The rainforest room is the closest thing I can think of to a steam room (except the surial bath, which is a bit different, wink, wink). They offer day passes to the rainforest room, not sure how much, but Barb and Tony have spa prices on their website at www.castawayclub.com
If you like steam rooms, you'll LOVE the Rainforest. Take a tour on embarkation day of the Rainforest room...and if you think you may use it more than once, get a length-of-stay pass.
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