a lantern. According to Geist, the Milan gallery and the roof were unprecedented in dimensions by previously built shopping arcades. Another difference with already existing passages, was the monumental character of the roof at Milan. Jodice, for example, appreciated the monumental spatial effect of the dome. In comparison to earlier emblematic arcades, such as Galerie d'Orléans (1828-1829) and Galeries Royales Saint-Hubert (1845-1847), the Milan arcade was also special because of the large spans of the vaults and the ethereal effect of the entire glass canopy. The construction of the whole Gallery was the result of international collaboration. This especially concerned the roof: the ironwork was produced, transported and installed by the French Atelier Henry Joret. The glass plates were made of flat ribbed glass by Saint-Gobain. The construction technology of the roof employs primary wrought-iron arches in order to support the glazing. By contrast, arcades that were built earlier were smaller and had simpler roofs: the same components were used for both load bearing and glazing purposes. In addition, the roof at Milan was equipped with invisible reinforcements in the supporting walls. This complicated roof is discussed as the unity of four systems that were skillfully combined through characteristic construction details. This construction technology was creative for avoiding visible tie-rods in the spans of the vaults and the dome, for a special effect of the glass plates and for the glazing bars. The historical roof was heavily damaged during the aerial bombings of World War II. Before that the roof had undergone multiple maintenance interventions. Serious problems in the roof were reported in the 1970s, and some of them were solved in the 1980s. The roof that we see today has gone through different historic modifications and represents complicated conservation issues. In 2015, in preparation for Expo Milano 2015, the facades, statues, and mosaics underwent detailed cleaning and repair, using a giant moving crane scaffolding system. Shops, restaurants and hotels The Galleria is often nicknamed (Milan's drawing room), due to its numerous shops and importance as a common Milanese meeting and dining place. As of 2013, the arcade principally contains luxury retailers selling haute couture, jewelry, books and paintings, as well as restaurants, cafés, bars, and a hotel, the Town House Galleria. The Galleria is famous for being home to some of the oldest shops and restaurants in Milan, such as Biffi Caffè (founded in 1867 by Paolo Biffi, pastry