The Medieval defensive walls have been silent witnesses of the tumultuous history of Namysłów. Construction of the walls began in 1350 at the initiative of the King of Bohemia, Charles IV, who also partially funded them. The walls were built with boulders and brick to a height of 8 m and crowned with 2-meter-high battlements. Some sections of the walls were 2.2 m thick. Earlier fortifications of the town, which have not survived, were probably made with earth and wood. According to historical sources, the walls used to have as many as 45 towers and castle towers. In the second half of the 18th century and in the 19th century, the obsolete fortifications gradually deteriorated and served as a source of materials for new buildings. A promenade was built in the old moat. The best-preserved sections of the walls can be found in the northern part of the town, along the Widawa river, and on the east at the Krakow Gate (Brama Krakowska).
In the vicinity of Piastowska street, close to the castle, there are two round-arch culverts through which one of the arms of the Widawa flows. This architectural solution resulted in the formation of the so-called Mill Island (Wyspa Młyńska) on the river.
In recent years, the walls in Staszica and Piastowska streets have undergone extensive repair and renovation works which have significantly improved their tourist appeal.