The Castle of Kalmar Along with the fortress of the Three Kronor, the Vyborg Fortress and Älvsborg Fortress is considered one of the top four Swedish castles. To begin building the castle was Canuto I of Sweden in 1100 that moved the citadel from the mainland reconstructing it on the island near the medieval port, enclosing it in a series of fortified towers. The works continued under Magnus Ladulås, which around 1280 raised the castle's actual dungeon. In 1337 Magnus Eriksson greatly expanded the castle, in particular the ground floor and built a further walled wall as well as a defensive portal on the main façade. In 1397 Kalmar Castle was at the center of one of the most important political events in the history of the Nordic countries: the Kalmar Union. The castle became the property of the mighty Margherita I of Denmark, which united under its rule Denmark, Sweden and Norway. Another woman who influenced politics a lot in Kalmar was Anna Eriksdotter, the castle's commander and ally of the crown of. At the end of the eighteenth century the castle entered a long phase of decline. Swedish historians count about 22 castle outlets distributed over three centuries, but it was never completely collapsed. On the other hand, many towers were damaged and the defensive capacity was greatly weakened. From 1766 he became a famous prison. Among the prisoners locked there, the most famous is Thomas Leopold, an exponent of Swedish radical pietism. The condition of the prisoners was poor and many died of scurvy because of the lack of clothing and the lack of heating in the winter. In the 1950s, by Oscar I of Sweden, a massive reconstruction phase began and the castle returned to its ancient splendor. At the end of the century the castle was founded by the Museum of Kalmar by Gustav Volmar Sylvander and at the same time began archaeological research excavations on the foundations of the castle and published several publications on its history.