Duke Eric (son of King Magnus III of Sweden) appears to be the first to construct a fortress in the southwest corner of Visby in 1310 as part of a struggle between his brothers for control over the kingdoms of Sweden and Norway as well as Danish claims on Gotland; this brings Gotland under Norwegian control.
Duke Eric, son of King Magnus III of Sweden, built a fortress in the southwest corner of Visby around 1310 during a conflict between his brothers for control over Sweden, Norway, and Denmark's claim to Gotland. This event resulted in Gotland coming under Norwegian rule.