The heart of the collection, and the first of the interventions carried out in the palace by Giorgio Franchetti, was the so-called Cappella del Mantegna, with the image of San Sebastian in the center around which the baron conceived a striking architectural space, entirely covered with marble. Inspired by Venetian models (especially the church of Santa Maria dei Miracoli), the room reproduces the atmosphere of a Renaissance chapel, ideally set inside a patrician residence. Above a real altar is the canvas, one of Mantegna's most dramatic inventions. The work, purchased in 1893, still constitutes the icon of the museum today, maintaining the arrangement desired by the owner unchanged within a museum itinerary that has undergone inevitable changes and revisions over the years. The late result of a study on the theme of martyrdom that Andrea Mantegna had already undertaken in the canvases today at the Kunsthistorisches Museum in Vienna and in the Louvre, the Ca 'd'Oro painting deals with the representation of the Christian hero in new and somewhat disconcerting terms. , of tragic individual isolation. The saint, pierced by sixteen arrows, which envelop him in a sort of thorny three-dimensional cage, stands sadly in the center of a narrow niche, framed by a faux marble frame. Below, on the right, a scroll wrapped around the emblematic image of the extinguished candle that still lets a thin wisp of smoke breathe, bears the inscription Nihil nisi divinum stable est coetera fumus (nothing, except the divine, is stable, everything the rest is smoke), to underline the fragility of human nature.