First time at a Korean spa, amazing! There are several rooms with different temperatures to choose from ranging from 0 to 90C as well as steam and bath rooms.
It is a naked shower facility meaning you are required to shower naked. I feel that the people who complain about it don't understand that cultural part. Bathing facilities including spas in most of East Asia are fully nude facilities. If you don't like it you can choose to go to a Western style spa.
The only thing bringing down the rating is that you're not allowed to bring food inside but they only serve instant noodles and snacks. It is a bit expensive but worth it if you go to relax and get away for a night.