Perhaps the most characteristic street of the Terzo di Città is the Via del Casato, or more simply the Casato, which, running a winding course, joins the Via di San Pietro with the Campo. This was once the most aristocratic street in Siena, where the nobles and wealthy Noveschi surrounded themselves with armed retainers and gave those sumptuous entertainments that were a feature in the social life of the "soft" city. There are still old palaces on either side; steep vicoli wind and radiate off from it, with sudden glimpses beyond of distant hills and towers. Where the present Palazzo Ugurghieri stands, and down the steep vicoli on either side, was once the palatial castle of the proud old house of the Ugurghieri, who, Lombard or Frank in origin, were descended from the Counts who in the ninth and tenth centuries governed Siena. Crossing the Campo, we enter the Terzo di San Martino at the Porrione, as the opening of the Via San Martino was called--a point of strategical importance in [Illustration: _Via della Fonte_] the furious factions of mediaeval Siena. At the corner of the Via Rinaldini (originally the Chiasso Largo, the street of the silk merchants) is the superb grey Palazzo Todeschini Piccolomini, the Palazzo de' Papeschi, as it was called, now the Palazzo del Governo, adorned with the arms of the Piccolomini and the Todeschini. It was built for the nephews of Pius II., the sons of Nanni Todeschini, by the Sienese architect, Pietro Paolo Porrini called Il Porrina, and begun in 1469; the _Ufficiali sopra l'Ornato_, on October 28th of that year, reporting to the Signoria that "the Palace begun by the Respectability of Messer Giacomo and Messer Andrea Piccolomini, will be a marvellous work and a most worthy ornament in your city, according to the intention and design of their Respectability."[141] The stone work, within and without, was for the most part carved by Lorenzo di Mariano. This palace now contains the Archivio di Stato of Siena; to do justice to its multifold interest, a book would be required larger than the present volume. In the Sala della Mostra a number of documents of all kinds are exhibited, illustrating Sienese life and politics from the year 736 downwards, including a whole series of Imperial diplomas from Louis the Pius in 813 to Charles V. in 1536. Here we may read, on the very parchment on which they were written, the letter from the Commune of Florence to that of Siena concerning the massacre of Cesena; the bull of Pius II., with a postscript in his own hand, exhorting the Sienese to admit the nobles to the government; Giovanni Torriani, general of the Dominicans, announcing his intention of sending Frate Girolamo Savonarola to Siena to reform the convent of Santo Spirito; or Cesare Borgia's ferocious threats of destruction from Pienza.[142] There are special series of autographs of famous ladies and of soldiers of fortune, as also of artistic documents, such as the agreement between