Rynek Glowny is located under the central square. The entrance is in the Sukiennice hall, just opposite the Church of Mary. In this museum you can see lots of artifacts, short movies, photos, a graveyard from the 1000th century and reconstructions of the former market stalls of Sukiennice. There's also a 6 km long multimedia exhibition, which shows you about the history of merchandise and transportation in the Krakow central square and town. Open 10AM-10PM, Sundays, closed. The allowed amount of people per day and per hour is limited, therefore it's better to buy the tickets forehand eg from the Krakow history museum's site. A museum worth seeing!