Sports Complex Station opens onto the Jamsil Sports Complex — Jamsil Baseball Stadium (home to the Doosan Bears and LG Twins) and the main stadium and arena where big concerts and events are held. Stadiums limit what you can carry in, so store your bag at the station first.
Coin lockers at Sports Complex Station
Sports Complex is a Line 2 / Line 9 transfer, with T-Locker coin lockers at 3 spots, about 101 in total. On the Line 2 side they sit near Exit 6 (about 53) and Exit 5 (about 39); on the Line 9 side there is a smaller bank toward Exit 9. See each spot and the live count by size on the Sports Complex 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.