The style of palaces and houses remained faithful to the older traditions. The public palaces were like castles. For centuries those of the Podestà and the Signory, for example, had been carefully strengthened and kept in a state of defence. From the towers, the bells of which summoned the citizens, there was a wide prospect over the city and its environs. The battlements, of the square form customary among the Guelfs, were adapted for defensive purposes. The windows on the ground storey were few and narrow, the gates were strengthened by double doors. The building material, consisting of heavy stones, or _macigni_, was furnished by the neighbouring stone-quarries of the hills of Fiesole and Golfolina on the Arno, at the spot where the river forces a narrow passage from the Florentine to the broad lower valley.[22] Great blocks of freestone, rough-hewn and gradually blackened by exposure to the air, formed those massive walls that seemed as though built for eternity. These walls have stamped their character on the later Florentine architecture; for the fifteenth and even the sixteenth century remained faithful to this _opus rusticum_, which has been transmitted down to our own days—modified, it is true, in its harsher features, but essentially unchanged. The windows of the upper storeys, divided first by slender marble columns, and then by various ornaments in the spaces of the pointed arch, relieve the gloominess of the fortress. The halls of the guilds and the palaces of the nobility exhibit the same style, though in them the embossments are partly or entirely smoothed away, and the windows are quite plain. Many of them are still preserved in the older quarters of the city, in the Borgo Sant’Apostolo, in the Via delle Terme, in the Mercato Nuovo, in the Via de’ Cerchi and Condotta, in the narrow streets behind the Old Palace in Via de’ Neri and de’ Rustici, and in Piazza Peruzzi, where they have even nestled in the Roman amphitheatre and elsewhere. The former palace of the Spini, between the Arno and the Piazza of Santa Trinità, the restoration of which has been undertaken by the present municipal authorities, presents, with its massive crown of battlements, the severe character of a fortress. The houses of the Mozzi at the south end of the Rubaconte bridge, and those of the Manelli on the Ponte Vecchio, among others, represent, in spite of change, the age of Dante; some, indeed, are now, after a lapse of six centuries, occupied by descendants of the very families that then possessed them.[23] The ground floors often show the traces of walled-up loggie, an indication of more peaceful days, for this style of building was continued even when party quarrels were fought out more by change of constitution and by proscription than by force of arms.