The Black Tower is one of the well-preserved remnants of the first wall circling Brussels. It can be seen at Place Sainte-Catherine, behind the church of the same name. In the 13th century, the city fortifications protected the centre of Brussels, around the Grand-Place. A second, larger, ring of fortifications was built later on. Remains of the first wall can also be seen at Rue des Alexiens and Boulevard de l’Empereur. The point where the River Senne flowed out of the city was very close to the Black Tower. In the 16th century, unlike other sections of the wall, the tower survived the creation of a new dock for the inland port of Brussels at the site where St Catherine’s Church now stands.