Architectural structures are often found in both in the monumen- tal and in the easel painting of Siena in the 15th century, but it is in the predella polyptychs that they enter into dialogue with human figures, creating harmonious compositions or original contrasts. In some works, they serve as a deco- rative background for narrative scenes, while in others they become integral parts of them. This article demonstrates that, despite the strong attachment of the Sienese artists of the Quattrocento era to the medieval tradition, it is in the predella polyptychs of the 15th century that innovations in the field of depicting architectural structures are adopted. Through the examination of a number of scenes from the predella of the sienese polyptychs, it became obvious that it was in the architectura picta that artists had greater freedom and depicted architectural innovations that had not yet been reflected in actual Sienese architecture. There are many predella fragments depicting architectural structures, but they have not been fully documented. The brief excursion reported in this study aims to review the most representative samples, organize them chronologically and analyze their evolution through almost the entire 15th century.