Built in the 19th century, Antwerp's Royal Museum of Fine Arts was conceived as a 'daylight museum' by architects Winders and Van Dyck. During the 20th century, the building underwent many fundamental changes in the layout, modifying the original circulation route and connection with the city. The latest intervention aims to reverse previous spatial changes by combining a thorough renovation of the historical museum with a contemporary extension concealed within the existing structure to highlight the heritage value and the resilience of the impressive 19th-century building. A complete overhaul of the 19th-century building restores the space's intrinsic qualities by reinstating original colours, materials, and routing within the historic halls. Guests can walk through an enfilade of exhibition rooms tinted in dark pink, green and red; oak doors, tall columns, and ceiling ornaments in plasterwork convey a feeling of ancient grandeur. The colour palette chosen during the renovation process directly relates to the original museum's colours. Meanwhile, hidden in the heart of the old building, a new vertical museum arises as a completely autonomous entity built within the four original patios. With bright white exhibition halls, hidden rooms, long staircases, and far-reaching sightlines, the new museum chart a route full of surprising vertical experiences. Daylight comes through triangular north-facing roof elements on the top hall and floods through four large lightwells. The high-gloss floors of the new museum add to the overall dazzling effect of these spaces. A sequence of strong vertical spatial experiences is created by dematerializing the visitor's experience and juxtaposing it with the building's historical identity. Wherever the new extension 'cuts' through the old museum, subtle marble inlays have been added, echoing the elegant 19th-century museum's materiality. Museum's solid mass with walls up to 70cm thickness make the thermal mass used to stabilize the inner climate, while the abundance of natural light reduces the need for artificial lighting. Additionally, a low volume ventilation system is discreetly implemented and requires 30% less air than a conventional full room climatization, resulting in equally les airducts and energy use. The new architectural concept of KMSKA is an adventurous journey where visitors explore the two contrasting and dialoguing museums sharing the ability to unveil themselves little by little. The 21st and the 19th-century museums could not be more different and intense, yet the extension coexists with the powerful historical structure without denying its monumental character. They embody an emblematic contrast in dimensions, light and atmosphere while being designed as flexible spaces to welcome future exhibitions. The visitor experience is never predictable and always in balance. Both routes are challenging and at the service of the art.