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.

At the entrance to Het Steen is a bas-relief of Semini, above the archway, around 2nd century. Semini is the Scandinavian God of youth and fertility (with symbolic phallus). A historical plaque near Het Steen explains that women of the town appealed to Semini when they desired children; the god was reviled by later religious clergy. Inhabitants of Antwerp previously referred to themselves as “children of Semini”. An organization concerned with the historic preservation of Het Steen and Semini, Antwerp Komitee Semini in Ere (AKSIE), formed in 1986, holds annual celebrations at Het Steen as cultural events.

At the entrance bridge to the castle is a statue of a giant and two humans. It depicts the giant Lange Wapper who used to terrorise the inhabitants of the city in medieval times.