This place is amazing! Definitely worth a stop if you're spending a few days in town. It's hard to know what to expect, so I'll break it down for you.

Info:

This is a local "swimming pool" - one of many in the area. There is an indoor pool as well as an outdoor pool. Outdoors, there is also a very large hot tub (can seat ~50), an ice tub (very cold water), two more hot tubs "hot pots" at different temperatures, and a steam room. The price is about $10 to get in. This is a very local place, so you won't see too many tourists, and be aware that there may be some school children running through (it was brief and they weren't too disruptive). The staff was very nice, and the locals didn't seem to care one way or another that I was there - the atmosphere is pretty quiet and relaxing.

Process:

You will enter the locker rooms and stow everything except your bathing suit and towel in the locker. Lockers are free. Make sure to bring your own bathing suit and towel, otherwise you will be charged a rental fee.

Do not put your bathing suit on. Proceed down the hall past the locker rooms and into the shower room. Put your towel and swimsuit on a shelf, and shower. It's the norm to shower nude, and there is often a staff member there to make sure you shower properly. It's normal for the culture - they're just trying to keep the pools very clean.

After you shower, leave the towel on the shelf, put on your bathing suit, and go enjoy the water. Locals will typically alternate between the hot tub, the ice bath, the steam room, the ice bath, the hot tub, etc. It's very relaxing!

After you're done, you must shower again (nude) and then you can collect you things and go.

All in all, a terrific experience!

*Also, the "rooftop hot tub" that google describes is a bit of a stretch - it might be elevated a floor but there are walls so you can't really tell. Don't expect a view or anything.

EDIT: there IS apparently a sauna. I must have missed it during my visit.