These two buildings were mapped as amenity=school. If they are the Orangerie, then they likely should be part of this school https://www.openstreetmap.org/way/1170532428 (which would become a multipolygon). See https://www.ecoleartuccle.be/ , where it says Château et Orangerie du Wolvendael
2, rue Rouge 1180 Uccle
The buildings also seem to share housenumber 11, but it wasn't immediately clear to me of which street