/usr/include/citygml/ is in libcitygml-dev 2.0.8-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/citygml/address.h
/usr/include/citygml/appearance.h
/usr/include/citygml/appearancetarget.h
/usr/include/citygml/appearancetargetdefinition.h
/usr/include/citygml/attributesmap.h
/usr/include/citygml/citygml.h
/usr/include/citygml/citygml_api.h
/usr/include/citygml/citygml_export.h
/usr/include/citygml/citygmlfactory.h
/usr/include/citygml/citygmllogger.h
/usr/include/citygml/citymodel.h
/usr/include/citygml/cityobject.h
/usr/include/citygml/enum_type_bitmask.h
/usr/include/citygml/envelope.h
/usr/include/citygml/featureobject.h
/usr/include/citygml/geometry.h
/usr/include/citygml/georeferencedtexture.h
/usr/include/citygml/implictgeometry.h
/usr/include/citygml/linearring.h
/usr/include/citygml/linestring.h
/usr/include/citygml/material.h
/usr/include/citygml/materialtargetdefinition.h
/usr/include/citygml/object.h
/usr/include/citygml/polygon.h
/usr/include/citygml/tesselator.h
/usr/include/citygml/texture.h
/usr/include/citygml/texturecoordinates.h
/usr/include/citygml/texturetargetdefinition.h
/usr/include/citygml/transformmatrix.h
/usr/include/citygml/vecs.hpp