The Visby city wall is a medieval defensive wall surrounding the Swedish town of Visby on the island of Gotland. As the strongest, most extensive and best preserved medieval city wall in Scandinavia, the wall forms an important and integral part of Visby World Heritage Site.Built in two stages during the 13th and 14th century, approximately of its original still stands. Of the 29 large and 22 smaller towers, 27 large and 9 small remain. A number of houses that predate the wall were incorporated within it during one of the two phases of construction. During the 18th century, fortifications were added to the wall in several places and some of the towers rebuilt to accommodate cannons.HistoryThe oldest part of the city wall is a defensive tower, today called the Kruttornet , which was erected at the harbor entrance in the 12th century, making it the oldest surviving non-religious building in the Nordic countries. It was not until the 1270s and 1280s, that the building of a proper defense for the town of Visby started, with the erection of the land-facing wall. This first wall was approximately tall. On the town-side, the wall had a raised platform for archers with regularly spaced openings for firing arrows while between the openings narrow there were arrowslits. According to dendrochronological examinations, the Österport was built no earlier than 1286, followed by two more in 1289: the Norderport and 1294 the Snäckgärdsporten . Around the 1290s and early 1300s, about 20 large towers were added between the gates.