Abstract: A curtain wall includes one or more vertically-extending mullions and one or more transoms, each extending horizontally between two mullions and having ends inserted in grooves of these two mullions. The curtain wall also includes at least an inwardly openable panel installed between two mullions, wherein a local adaptation of the two mullions adjacent to the openable panel comprises at least the removal of a laterally directed wall of the inner chamber of each of the two mullions along a height of the openable panel, and wherein the openable panel is installed in the local adaptation of the two mullions adjacent to the openable panel such that, when the openable panel is closed, the openable panel is not distinguishable from a fixedly fitted panel, neither from the inside nor from the outside of the curtain wall.