Grote Markt originally was a forum or square just outside the medieval residential quarter. In 1220 Duke Henry I of Brabant (1165-1235) donated this community land to the city.
The name Merckt was used for the first time in 1310.
Around this time the first annual markets or foren van Brabant (Brabant fairs) were organised. Here English merchants would do business with Italians, Spaniards and merchants from the Northern German Hanseatic cities as well as from Southern Germany and Flemings of course. At the end of the fifteenth century Antwerp overtook Bruges as the most prominent city of the Low Countries.
https://www.visitantwerpen.be/en/sightseeing/grote-markt