A long underground stretch next to the Express Bus Terminal, easy to find. There is one shop after another, small stalls, non branded, selling everything from underwear to nights gowns. Surprisingly prices are extremely reasonable, for USD 5 onwards one can find something. It can be very crowded and noisy, not a serene shopping experience. Most shops are directed towards ladies wear, gents wouldn't find much there. It is quite iconic for Seoul though and worth a visit.