The Hôtel Gaiffier d’Hestroy, a historic 17th-century house, is one of the most significant works of Namur’s architectural heritage. Since 1964, it has also housed the Museum of Ancient Arts, whose collection focuses on the magnificent 13th-century Oignies Treasure.The proposed extension project can be seen as a reflection of the layout of the original building, with the existing front courtyard and the new inner courtyard highlighting the hotel as the true architectural protagonist. The project conceives of the Oignies Treasure as the symbolic and formal origin of the whole. As if it were a hidden chest, a circular drum located in the basement in line with the historic hotel constitutes the central point around which the new exhibition spaces gravitate.The Hôtel Gaiffier d’Hestroy will be the starting point of the museum tour, connecting it to the new extension, which will be located on two underground levels and two above-ground levels. In this way, the large volume required is largely hidden from the outside, reducing the scale of the new intervention in relation to the historic building. The temporary exhibition room occupies the lower level of the extension, while the workshop and mediation space are on the upper level, with natural light. The need to be able to carry out the work in two separate phases is resolved by the proposed layout, with double access from Rue de Fer and from Venelle des Capucines, which will allow it to operate independently during the construction period. The new contemporary intervention will appear in the historic city of Namur while respecting and enhancing the original architecture of the Hôtel Gaiffier d’Hestroy, establishing a dialogue with the memory of the place, with the Trésor d’Oignies and with the precious works exhibited there.