Visby City Wall (, "Visby Ring Wall", sometimes Visby stadsmur, "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. History The oldest part of the city wall is a defensive tower, today called the Kruttornet (the Gunpowder Tower), 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 narrow openings there were arrowslits. According to dendrochronological examinations, the Österport (the East Gate) was built no earlier than 1286, followed by two more in 1289: the Norderport (North Gate) and 1294 the Snäckgärdsporten (the Snäckgärds Gate). Around the 1290s and early 1300s, about 20 large towers were added between the gates. The construction of the wall was probably connected to conflicts that arose between the town of Visby and the thing or assembly of Gotland, which led to a civil war on the island in 1288. A part of the wall east of Kvarntornet (the Mill Tower) which has been razed possibly dates from the beginning of this war, when Visby was captured and plundered. Construction of city walls was unusual in Nordic countries during the Middle Ages, and so the construction of the city wall testifies to Visby's commercial importance during this time. In medieval Sweden, only Stockholm, Kalmar and Visby had city walls. The last major rebuilding of the city wall occurred in the 1350s, when the wall was strengthened and its height increased