Numerous details indicate that Baldassare Peruzzi made this design for an altar as a presentation drawing, to be shown to a patron for approval. He took great care when drawing the altar's intricate decoration, meticulously outlining the scrolling rinceaux pattern interlaced with animals along the frieze and base of the columns and carefully shading the delicate fluting, dentils, and egg-and-dart motifs. He also showed the effects of shadows on the top and right parts of the altar frame and noted the size of various components on the design so that this large altar could be built with precision.
Although this drawing does not relate to any known structure, it probably represents an unexecuted design for a side altar for the cathedral of Siena. Three of the saints in the niches appear facing to the right, toward the main altar, indicating that this altar would have stood in the left aisle.