Het Steen is a medieval fortress in the old city centre of Antwerp, Belgium, one of Europe's biggest ports. The surviving structure was built between 1200 and 1225 as a gateway to a larger castle of the Dukes of Brabant which was demolished in the 19th century. As the first stone fortress of Antwerp, Het Steen is Antwerp's oldest building and used to be its oldest urban centre. The words "Het Steen", are dutch for The Rock. The first documented mention of Antwerp Castle dates back to the 12th century. However, there was a castle here as early as the Carolingian period in the 9th century. The first castle may have been built after the Viking incursions in the early Middle Ages; in 879 the Normans invaded Flanders. The Margraviate of Antwerp came into being around 974. The Duchy of Lower Lotharingia was part of the Holy Roman Empire, while on the opposite bank of the Scheldt lay the county of Flanders, which was subordinate to the king of France. From 1076 to 1100 Godfrey of Bouillon was the Margrave of Antwerp. Godfrey I, Count of Louvain, received the duchy in 1106. His great-grandson was Henry I, Duke of Brabant who received the Duchy of Brabant in 1183. Previously known as Antwerpen Burcht (fortress), Het Steen gained its current name in around 1520, after significant rebuilding under Charles V. The rebuilding led to its being known first as "'s Heeren Steen" (the King's stone castle), and later simply as "Het Steen" (the stone castle). The Dutch word "steen" means "stone", and used to be used for "fortress" or "palace", as in the "Gravensteen" in Ghent, Belgium. The fortress made it possible to control the access to the Scheldt, the river on whose bank it stands. It was used as a prison between 1303 and 1827. The largest part of the fortress, including dozens of historic houses and the oldest church of the city, was demolished in the 19th century when the quays were straightened to stop the silting up of the Scheldt. The remaining building, heavily changed, contains a shipping museum, with some old canal barges displayed on the quay outside. In 1890 Het Steen became the museum of archeology and in 1952 an annex was added to house the museum of Antwerp maritime history, which in 2011 moved to the nearby Museum Aan de Stroom. Here is also a