The Palazzo Pubblico (town hall) is a palace in Siena, Tuscany, central Italy. Construction began in 1297 and its original purpose was to house the republican government, consisting of the Podestà and Council of Nine.
The outside of the structure is an example of Italian medieval architecture with Gothic influences.  The lower story is stone; the upper crenelatted stories are made of brick.  The facade of the palace is curved slightly inwards (concave) to reflect the outwards curve (convex) of the Piazza del Campo, Siena's central square of which the Palace is the focal point.  The campanile or bell tower, Torre del Mangia, was built between 1325 and 1344 with its crown designed by the painter, Lippo Memmi.  The tower was designed to be taller than the tower in neighboring rival Florence; at the time it was the tallest structure in Italy.  It was fitted with a mechanical clock during the mid 14th century.  Its design has been used as the basis for several other campaniles including the Dock Tower in Grimsby, England constructed in 1852 and the Joseph Chamberlain Memorial Clock Tower in the edgabston campus of the University of Birmingham (completed in 1908).
The Copenhagen City Hall and Odense City Hall, Denmark, were greatly inspired by Palazzo Pubblico. 


Nearly every major room in the palace contains frescoes.  These were unusual for the time in that they were commissioned by the governing body of the city, rather than by the Church or by a religious fraternity.  They are also unusual in that many of them depict secular subjects instead of the religious subjects which are overwhelmingly typical of Italian art of this era.
The most famous of the secular frescoes are three panels in the series on government in the Hall of the Nine (also known as Sala della Pace) by Ambrogio Lorenzetti.
These frescoes are collectively known as The Allegory of Good and Bad Government.
The Allegory of Good Government depicts the personification of Justice as a woman.  She gestures to the scales of balance, held by the personification of Wisdom floating over her throne.  On the viewer's left, a convicted criminal is beheaded; on the right, figures receive the rewards of justice.  At Justice's feet, the personification of Virtue, also, unusually for the time, portrayed as a female figure, passes virtue among twenty four faithfully rendered and recognizable images of prominent male citizens of Siena.  The men face towards the largest figure in the image, a judge located in the center right.  The judge is surrounded by additional personifications including Peace, who is represented as a fashionable, white-clad contemporary female figure with elaborate blonde hair.
The allegory carries a strong social message of the value of the stable republican government of Siena.  It combines elements of secular life with references to the importance of religion in the city at the time.  The figure of Justice resembles the figure of Mary, Queen of Heaven, the patron saint of Siena, on a throne.  The Judge reflects the tradition in the Christian Last Judgment to have God or Christ judging the saved on the left; the damned on the right.  While classified as medieval or proto (pre)-renaissance art, these paintings show a transition in thought and an evolution in theme from earlier religious art.
Flanking the Allegory are two other paintings on perpendicular walls: Effects of Good Government and Effects of Bad Government.  Both these frescoes depict a recognizable view of Siena and its countryside.
In the allegorical representation of Good Government, the prosperous townspeople are trading and dancing in the streets.  Beyond the city walls is a lush countryside in which crops are harvested.
In the allegory of Bad Government, crime is rampant and diseased citizens roam a crumbling city.  The countryside suffers from drought.
Many of the frescoes in the Palace, including these, are badly damaged.  This is allegedly due to salt once stored in the basement of the building.  It is theoretically possible that the salts wicked moisture down from the walls, causing the plaster to dry excessively and the frescoes to flake off.
Other notable frescoes include the mysterious fresco of Guidoriccio da Fogliano at the siege of Montemassi, located in the Great Council Hall (Sala del Mappamondo). The fresco is traditionally attributed to Simone Martini, although there is debate on the subject.  The wall has circular markings left by the circular wall-mounted (now lost) map of the world by Ambrogio Lorenzetti.
Siena was decimated by the Black Death in 1348.  Approximately half the population died in the plague.  The republic's economy was destroyed and the state quickly declined from its position of prominence in Italy.  The Franciscan religious order rose to power in the city.  The stagnation over the following centuries meant that while Siena did not develop during the Renaissance as did other Italian cities, it was also preserved both from bombardment during World War II and from modern development.