By 1183, Coudenberg played a leading role in the new Duchy of Brabant. By 1356, the castle had become a residential palace and in the 15th Century, Philip the Good added a series of new annexes, extended the gardens and built an enormous room, the Aula Magna, to hold state functions in it. Over the years the castle witnessed many historic events including some notable abdications. In 1731, a fire raged through the castle kitchens, it spread at such pace that the whole palace was consumed by fire ruining many of the great masterpieces that had adorned the walls. The only thing to survive was the Gothic chapel, but this was later demolished when Charles Alexander of Lorraine wanted to replace the ruined castle with a Royal Square.

Today, after several years of excavation, the remains of the palace foundations can be seen at the Bellevue Museum, which stands on the site of the old castle. The Bozar centre and the northern corner of Place Royale now stand on the site originally occupied by the chapel and Aula Magna. Many of the cellars have been preserved including those beneath the banquet hall in the Aula Magna and the chapel.