WA Viking ring fortress, or Trelleborg-type fortress, is a type of circular fort of a special design, built in Scandinavia in the Viking Age. They are also known simply as trelleborgs. All trelleborgs have a strictly circular shape, with roads and gates pointing in the four cardinal directions. These common structures are sometimes partially encircled by advanced ramparts, but these additions are not always circular.
WAggersborg is the largest of Denmark's former Viking ring castles, and one of the largest archaeological sites in Denmark. It is located near Aggersund on the north side of the Limfjord. It consists of a circular rampart surrounded by a ditch. Four main roads arranged in a cross connects the castle center with the outer ring. The roads were tunneled under the outer rampart, leaving the circular structure intact.
WBorgeby Castle lies in Lomma Municipality, Scania in southern Sweden, beside the Kävlingeån, the largest river in Scania.
WFyrkat is a former Viking ring castle in Denmark, dating from c. 980 AD. It is located near the town of Hobro, some distance from the present end of the Mariager Fjord in Northern Jutland. The fortress is built on a narrow piece of land, with a stream on one side and swampy area on the other sides. It would have enabled control of the traffic on the main land route between Aalborg and Aarhus.
WNonnebakken is a hill in Odense, Denmark. It is the site of one of Denmark's six former Viking ring castles, built during the reign of Sweyn Forkbeard, who had forced his father Harold Bluetooth to leave the country and seek refuge with the Jomsvikings on Wollin around 975. The fort enabled its occupier to control the Odense River passing next to the hill.
WTrelleborg is a town in Skåne, Sweden, with 43,359 inhabitants as of December 31, 2015. It is the southernmost town in Sweden located some 10–15 kilometres (6.2–9.3 mi) west from the southernmost point of Sweden and the Scandinavian peninsula. It is one of the most important ferry towns in Scandinavia as well as around the Baltic Sea, and the main town of the Söderslätt agricultural areas.
WThe Trelleborg west of Slagelse on the Danish island of Zealand, is one of seven Viking ring castles discovered as of 2014. In its day, the fortress was situated on a peninsula that jutted into the swampy area between two rivers. The swamp was connected to the Great Belt by a lake that at its time could be navigated by Viking ships. Trelleborg is believed to have been ordered by King Harald Bluetooth in the year 980 AD and it might have commanded the Great Belt and its sea traffic, between the islands of Zealand and Funen.