Insadong, Jongno and the palaces are Seoul's old centre, full of hanok guesthouses. The bathhouses here are old-style neighbourhood mogyoktang, some of them decades old, plus a few hanjeungmak. For a full jjimjilbang, Myeongdong and Dongdaemun are each about 2 km away.
Most places on this list are ordinary neighbourhood bathhouses with signs in Korean only. These guides explain what to do at the counter, what it costs and the rules on tattoos.