Het Steen is a medieval fortress in the old city centre of Antwerp, Belgium, one of Europe's biggest ports. Built after the Viking incursions in the early Middle Ages as the first stone fortress of Antwerp, Het Steen is Antwerp's oldest building and used to be its oldest urban centre.Previously known as Antwerpen Burcht (fortress), Het Steen gained its current name in around 1520, after significant rebuilding under Charles V.