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BUILDING EXTERIOR 61▲ 4.15 Library Square, Vancouver,Canada, Moshe Safdie andAssociates Inc., 1995. A gap revealsthe cross-section of the screeningframe and a glimpse of the mainlibrary block behind.▲ 4.16 Getty Center, Los Angeles, USA,Richard Meier & Partners, 1997. Exteriorstructure deepens the rear of the Rotunda.While less overt at the Getty Center, Los Angeles, structural elementsplay important screening roles in many locations around the museumcomplex. In some cases by varying the relative positions of structure andskin in plan, structure projects beyond the building enclosure to contributedepth and to some extent screen the façades. This strategy canbe observed where the Rotunda backs onto the Museum Courtyard(Fig. 4.16). The exterior columns of many buildings are exposed and actas counterpoints to adjacent walls. In other areas, exterior colonnadesthat support canopies or walkways enrich the experience of walkingbeside the buildings (Fig. 4.17). This layering of structure in front of thefaçades deepens them and effectively screens them, successfully reducingthe undesirable visual dominance of potentially large areas of bare wall.▲ 4.17 A colonnade supporting anelevated walkway alongside an externalwall.Compared to the relatively deep structural screens at the MelbourneExhibition Centre, Library Square, and to a lesser extent the GettyCenter, most screening structure on the main façade of the CentrePompidou, Paris, lies within a vertical plane (Fig. 4.18). Located in frontof the building envelope a distance almost equal to the length of a gerberette,5 the screen consists of slender horizontal tubes and vertical anddiagonal tension rods. The exterior structure, mainly resisting tensionforces, is so fine it risks being misread as scaffolding. Although ineffectiveas a screen or filter for natural light, the large number of members and