In the Middle Ages, Krosno Odrzańskie was probably surrounded with bulwarks made with soil and timber, which were replaced by defensive walls at the end of the 13th Century. Built mainly with brick, supplemented by boulders, the walls used to encompass the entire town like a ring. There were three gates in the walls: the Oder Gate (Brama Odrzańska), the Głogów Gate (Brama Głogowska) and the Stone Gate (Brama Kamienna). In 1633, in the middle of the Thirty Years’ War, the walls were reinforced and the town was made into a fortress. However, the defensive walls started to gradually decline before the 17th Century was over and were nearly completely dismantled in the second half of the 19th Century.