The facing is made of Candoglia marbles (pink and white), while the statues and the decorative works are made of Carrara marble (white). Other pre-Alpine stone materials were used, such as Simona sandstone, Saltrio limestone, Oira stone (serpentinite). Varenna and Verona limestones were used for their different colors (purple, grey, green, black, and red). The reused materials (red and green porphyry from Egypt) have a decorative aim. The state of preservation is different according to the mineralogical composition and the texture of the stones and their finishing: Candoglia marble shows superficial corrosion, the Carrara marble shows decohesion and pulverization; the Simona sandstone shows much scaling.