The cubical building is built in solid rusticated stonework, with two rows of two-lighted Gothic windows, each with a trefoil arch. Michelozzo Michelozzi added decorative bas-reliefs of the cross and the Florentine lily in the spandrels between the trefoils. The building is crowned with projecting crenellated battlement, supported by small arches and corbels. Under the arches are a repeated series of nine painted coats of arms of the Florentine republic. Some of these arches can be used as embrasures (spiombati) for dropping heated liquids or rocks on invaders.
Duke Cosimo I de' Medici moved his official seat from the Medici palazzo in via Larga to the Palazzo della Signoria in May 1540, signalling the security of Medici power in Florence. The name was officially changed after Cosimo removed to Palazzo Pitti, renaming his former palace the Palazzo Vecchio, the "Old Palace", although the adjacent town square, the Piazza della Signoria, still bears the old name. Cosimo commissioned Giorgio Vasari to build an above-ground walkway, the Vasari corridor, from the palace, through the Uffizi, over the Ponte Vecchio to the Palazzo Pitti.