The Sienese merchant Ambrogio di Nanni Spannocchi’s decision in 1471 to build his family palace in the area adjoining the former Salimbeni property arose from his desire to legitimate the political and economic power his family had achieved thanks to its mercantile and banking activities and to the fact that Pope Pius II, a member of the Piccolomini family, had chosen them as his treasurers. Work began in 1473 under the direction of the Florentine architect and sculptor Giuliano da Maiano. Along with the Palazzo Piccolomini built by Bernardo Rossellino soon after the middle of the fifteenth century, the building designed by Giuliano da Maiano represented for Siena a real innovation and a profound break with the schemes and architectural types of a typically Gothic urban environment. The front of the palace is organized in three storeys; the ground floor is marked off rhythmically by five round arches, echoed on the upper storeys by an equal number of two-light windows divided by elegant colonnettes. The ashlar-work decoration, elegant design of the windows, and proportional criterion used to distribute the elements of the façade recall the architectural language worked out by Michelozzo for the Medici Palace in Florence. The great cornice crowning the façade also takes its inspiration from the cornice at the top of the palace built for Cosimo the Elder. In Palazzo Spannocchi, however, the citation of classical antiquity was given a new element by the adoption of sculptural elements as ornamentation (the sculpted heads of ancient Roman emperors). On the interior, Palazzo Spannocchi has an open inner courtyard, surrounded by a spacious gallery; the reference is evident to the atrium of Roman patrician homes. From this area, reserved for the Spannochi storerooms and warehouse, rose an elegant stone staircase which led to the upper residential floor.