A 10th century medieval fortress, the city's oldest building. It was from the 16th Century on for 3 centuries the prison of Antwerp.  Until 2008 it was the National Maritime Museum,.  The Steen is now closed.  The City of Antwerp has for the moment (oct 2009) no future plans for the Steen Castle.

As from May 2011 the National Maritime Museum will be housed in the new MAS (Museum Aan de Stroom).