Among my experiences with listed buildings, the complete reconstruction and extension of the Belgian consulate and residence building in Budapest (3,500 m², below Buda Castle) stands out. The task was, on the one hand, to preserve the historically valuable part of the building and emphasise its main virtues; on the other, to design a new architectural identity in place of the less valuable part to be demolished, and — for the sake of unity — to create an ensemble with a fresh architectural value of its own. This aim applied not only to the design process but to the construction as well. With a listed building, something unexpected always arises during demolition and rebuilding that cannot be planned on paper or found in the original drawings. In such moments the most suitable solution must be found from the architectural, technical and heritage points of view — even though these considerations are often at odds with one another.