In the 1970s major architectural renovations were undertaken, giving rise to a model installation that remained virtually intact for more than 30 years. The refurbishment introduced profound changes such as the removal of the roofs over the courtyards, which were reduced in size and turned into gardens. Above all, however, it provided an opportunity to expand the exhibition area and improve the flow of visitors through the building. The renovations enhanced the security, conservation and illumination of the collections, and ultimately the way they were presented.