City Hall sits in the heart of downtown Seoul — Deoksugung Palace with its changing-of-the-guard ceremony, Seoul Plaza, the historic Jeongdong-gil, and the old City Hall that is now the Seoul Metropolitan Library. Store your bag and stroll it all light.
Coin lockers at City Hall Station
City Hall is a Line 1 / Line 2 transfer, with T-Locker coin lockers at 3 spots, about 69 in total — near Exits 2 and 3 (about 28) and Exit 1 (about 16) on the Line 1 side, plus about 25 by Exit 8 toward the Line 1 transfer. See each spot and the live count by size on the City Hall Station page.
Prices are the same across Seoul — about ₩2,200 (small) to ₩4,400 (large) for four hours, then hourly. English screen, pay by card, no ID.