Palazzo Castiglioni was built by Giuseppe Sommaruga and constitutes a splendid example of Art Nouveau in Milan. The ashlar base of the building takes up the natural shape of the rock while the other decorations are in stucco, echoing the eighteenth-century style. The client, Ermenegildo Castiglioni in 1900 decided that he would have a building that would stand out compared to the usual buildings thanks to interesting solutions. Liberty style was exactly what he was looking for. When the scaffolding was removed in 1903, two large statues on the sides of the door (by Ernesto Bazzaro) stunned the thoughtful of the time. The female figures, allegories of peace and industry, were prosperous and half-naked women. This scandalized the well-thinking of the time and the palace was sarcastically renamed "Cà di Ciapp" or palace of the buttocks. The statues were then removed and are now located on Villa Facanoni (in via Buonarrotti 48) on the sides of a secondary entrance. The Portal was then modified with the addition of a bas-relief to make up for the lack of these two statues.
The whole history of the building can be read in the monograph "Giuseppe Sommaruga (1867-1917). A progragonist of Liberty", edited by Andrea Speziali, CartaCanta editore 2017.