Jjimjilbang. EAT, Sleep, and Bathe.
 

For details about where to stay for cheap in Korea, stay at Jjimjilbang.


http://english.visitkorea.or.kr/enu/...jsp?cid=626600

In Korea, the Jjimjilbang-Korean Spa is a place where one can enjoy the spa, shower, and sauna but also sleep overnight at an affordable price. They are a popular getaway for Korean families, couples, and friends. You can enter various heated rooms each designed with a particular theme. These are great places to sweat and relax.

In a Jjimjilbang-Korean Spa, you will also find many recreational facilities such as a snack bar, fitness club, PC bang, and noraebang. One can have a fun time in a Jjimjilbang-Korean Spa at any time, whether the weather is hot, cold, or rainy, or when one feels bored. Open 24 hours a day, Jjimjilbang-Korean Spa have already become well known among foreign travelers as a clean and affordable place to stay overnight and relax after an intense day of sightseeing. Join visitkorea as we visit two of Seoul’s most famous Jjimjilbang-Korean Spa.

You posted a description of it but you want more? Well, I can say that they might be a budget way to spend the night in the ROK. Not that I wanted to, but all of the hotels by Incheon Airport were booked, so a local led me to a jjimjilbang. I think the cost was around ₩9000, or about US$8, and it came with a locker, use of the bathing facilities, toothbrush, and uncomfortable (and not too quiet) but nonetheless cheap common sleeping area. Separated by gender. For the price and moment of desperate need, it was ok enough.

Jimjilbang are also used for accomodation by homeless and other troubled Koreans at least in Seoul. That's probably why a lot of them are at least not officially 24h.