A traditional part of the Medieval Week on Gotland is the story of Visby and Waldemar Atterdag, King of Denmark. I can recommend the following book to read all about what actually happened in Visby in 1361: "Visby 1361 INvasionen" By Gun Westholm. The book is in Swedish only. ISBN.978-91-518-4568-5.
What happens at Medeltidsveckan is a reenactment of Valdemar Atterdag’s wrongful entry into Wisby, with lots of action. Then there is a scene at Stora Torget: Valdemar Atterdag overtaxes Wisby’s citizens.
