The Counts Guidi built the medieval nucleus of the Palagio Fiorentino in 1230 and they transformed it into their residence. The Guidi of Palagio were a branch of one of the most powerful feudatory dynasties in Arezzo. They had established their influence on the territory of Stia since the XIII century and dominated it for two centuries.

In the Modern Age, not much remained of the original structure, because it underwent decadence and the consequences of the Guidi's extinction. At the end of the XIX century, the advocate Carlo Beni bought its remains and its surrounding territory with the aim to re-establish its magnificent ancient structure. The architect Giuseppe Castelucci was charged with supervising the works and with planning the new palace as similar as possible to the medieval feudatories' ancient mansion.
The castle was conceived as an original mix of Late-Romanesque and medieval elements. For instance, its façade shows the strong influences of the XIX-century art, but some parts of its structure, such as the stairs connecting the floors, were inspired by the castle of Pioppi's architecture. The decorations are mixed, too. As a matter of fact, the emblem of the Guidi stands out on the lintel and on the capitals, even if the latter are supported by two columns with an evident modern manufacture.
Castellucci provided for the drawing of the Palagio's interiors in a personal and original fashion. The plan was probably conceived to recall the Guidi's fortress, while part of the furnishing in the halls and in the rooms are emblems, fireplaces and ancient washstands that fitted well the spirit of the historical reconstruction lying at the base of the work and the criteria established by the architect Castellucio and by Beni.
The Palagio that today belongs to the Municipality of Stia houses the Museum of Contemporary Art, the Ornithological Museum "Carlo Beni" and numerous cultural manifestations and meetings that take place in Stia each year. In the rooms dedicated to contemporary art, almost 200 works of art, paintings and sculptures by great masters like Pietro Annigoni, Primo Conti, Mino Maccari, Marino Marini, Giò Pomodoro and Ottone Rosai, are exhibited.