After reviewing a post and comments from you lovely readers I found a new 24-hour jjimjilbang not far from the Jayang-dong Happy Day Spa. This new find is called Riverside SpaLand (강변스파랜드) and gets 10 stars on Daum, but only 5/10 on Naver. You can find it just behind the East-Seoul intercity bus terminal (동서울 종합터미날), out exit 4 from Gangbyun Station. From the looks of the building it seems like a nice, large facility. The jjimjilbang shares the building with Sungjin Leisure Sports health facility. Check out the Official Site of Korea Tourism's page about Riverside SpaLand as well.
It encompasses 7 floors with a roof-top area to cool off or catch some rays this summer. In the sauna are the usual hot, warm, cool, and event baths, along with a hinoki wood bath and a walking-track/massage bath. Add two sweating rooms - humid and dry - and you've got a complete sauna. In their jjimjilbang, there are many interesting rooms. There are two traditional Korean sweating caves, one of which is made from wood; first time I've seen this. Then your usual salt, yellow soil (hwangto), and charcoal rooms, pine room, silver pyramid, fresh oxygen room, and an ice igloo. Oh, and my favorite: sleeping caves! With these and all the rest area, you'll have plenty to keep you occupied for the day.
서울 광진구 구의동 593-15
Seoul, Gwangjin gu, Gu-eui dong, 593-15
Open 24 Hours
Day hours: 5AM to 8PM
Adults 7,000 Children* 5,000
Overnight: 8PM to 5AM
Adults 9,000 Children 6,000
*Children under 7 (Entrance is for 12 hours, 1,000 won per hour after. But if you stay past 15 hours you'll be charged a flat rate of 7,000 for the time beyond 12 hrs.)
Wikimapia of Riverside SpaLand