The Viking ring fortress of Trælleborg is located on the island of Sjælland (Zealand) in Denmark. Situated in the proximity of the small town of Slagelse, the fortress is one of the five of its kind built in Denmark during the Viking Age. The other ring fortresses in Denmark dating back to the Viking Age discovered as of 2014 are Aggersborg (located in the proximity of Limfjorden, northern Jutland), Borrering, Fyrkat and Nonnebakken. There are also two Viking age ring fortresses in Sweden, one situated in the locality of Trelleborg, Scania, and the other one in Borgeby (located northward of Lund, in the same southern Swedish province of Scania), as well as a possible one in Norway in Rygge, near Østfold. The Trelleborg ring fortress is dated 1000 AD, but other estimations put its construction at 981 AD.