Palazzo della Ragione stands at the centre of Padua, within the city's ancient thirteenth-century belt of walls.
The 13th and 14th centuries were a time of splendid flourishing for Padua, thanks to the development of commerce and craftsmen's activities as well as the political stability brought about by the new form of government, the Commune. During those years numerous religious buildings were erected or enlarged, among them the Scrovegni Chapel, the Church of the Eremitani and the Baptistery of the Cathedral, decorated with grandiose cycles of frescoes.
Palazzo della Ragione was the symbol of Communal power and the centre of the city's markets, but above all the place where justice was administered.
Its interior is decorated with a great astrological cycle composed of over three hundred panels arranged in three bands, inspired by the doctrines of the physician, astronomer and astrologer Pietro d'Abano and originally painted by the greatest artist of the time: Giotto.
Palazzo della Ragione, which has also been called a 'ship to sail the skies', thus became a 'prediction machine', a microcosm in which human activities were judged taking into account the influence of the celestial bodies.

In the 13th century, the appearance of Palazzo della Ragione was very different from what we see today. Originally, the upper floor was divided into three sections, with a central hall in which four columns supported a trussed roof.
In the early years of the 14th century Fra' Giovanni degli Eremitani remodelled the palace, introducing two new elements: the roofing and the two-floor loggias.
For the first time, a roof in the shape of an upturned ship's keel was used on a public building, an element that was to become the most distinctive feature of Palazzo della Ragione.
In 1420 a fire broke out on the mezzanine floor, destroying much of the building. The wooden structures that supported the flooring of the hall known as the Salone and the ceilings of the loggias were replaced by brickwork vaults. In addition, the partitions in the Salone were removed, making it a single vast room. During this same period, the city's flourishing commercial activity led to the addition of two porticoes, one on the north, the other on the south side of the building. After the fire, the star-strewn sky that had been painted on the ceiling was restored.
Another traumatic event in the history of the Palazzo occurred in 1756, when a whirlwind destroyed much of the roofing over the Salone and the northern loggia. Only the ceilings of the southern loggia remain frescoed, while those on the northern side were rebuilt.
In 1797 the Palazzo ceased to serve as seat of the courts of justice and began to be used for temporary events. Memorable in this respect are the scenic decorations of Giuseppe Jappelli installed for the visit of the Austrian Emperor Franz I of Hapsburg in 1815.

The insignia of the courts of justice, painted starting from 1271, are the oldest decoration in the Salone, along with the representations of the Theological and Cardinal Virtues and the Trial of Pietro d'Abano, dating from between 1370 and 1380. All of these frescoes are found in the lower band running around the four walls of the room.
Let's observe in detail the insignia in the Court of the Fox, where the contract for decorating the Ovetari Chapel was signed by Empress Ovetari and Andrea Mantegna. These insignia derive mainly from medieval bestiaries, moralizing books based on the ancient tradition that each animal possessed virtues and vices that could be related to human characters.
The fire of 1420 also destroyed the astrological cycle painted by Giotto. Niccolò Miretto and Stefano da Ferrara repainted these frescoes, which can still be seen today.
In the various panels that make up the sky, appearing in the upper band running around the four walls are the Constellations, the Planets, the Influxes of the planets, the Signs of the Zodiac, the Influxes of the zodiac signs, the Months and the Influxes of the months. Of the twelve zodiac signs, let's look closely at Cancer and Aries. Both signs are found on the south wall; the position of Aries, in proximity to the southeast corner, is especially interesting. In the past, the beginning of the year was made to coincide with the reawakening of nature; the astrological year as well begins with the spring equinox, in the month of March, and thus under the sign of Aries associated to it.
The decoration can be divided into twelve sections, corresponding to the months of the year. In each are represented an Apostle, the sign of the zodiac, the personification of the month, the representation of the planet domiciled in it, the influences exerted on the characters and activities of human beings, and the extra-zodiacal constellations. Among the seven planets, let's examine in detail Jupiter in Sagittarius and Mars in Scorpio, found on the northern wall.
Among the constellations depicted in the cycle of frescoes, determinant in the life of every individual according to the aspect they assume at the moment of his or her birth, let's look more closely at Pegasus, on the east wall, and Aquila, on the northern one. Among the personifications of the twelve months, we may observe in particular August, found on the west wall, and April, on the south wall.

The astrological concept described in the pictorial cycle derives from the codifying of direct observations of the sky made in antiquity. In 150 A.D., Ptolemy devised an abstract model of the zodiac divided into twelve equal parts, although in reality there are thirteen constellations occupying different sectors of the ecliptic, that is, the apparent orbit of the sun. However, this codifying failed to take account of the so-called precession of the equinoxes, a phenomenon known since antiquity, in which the changing oscillation of the earth's axis inclined by 23°27' in relation to the ecliptic results in retrocession of the equinoxial points.

The astrological cycle in Palazzo della Ragione can be interpreted as a treatise on astrology, where the constellations of the zodiac explicitly evoke the image of the ecliptic.
The significance of some figures in the Paduan cycle is sometimes difficult to decipher. Analogies with medieval astrological texts suggest them to be paranatellonta, that is, extra-zodiacal constellations or parts of constellations that accompany the rising of the sun each day.
In analysing the constellation of Taurus, we can verify analogies in the positions of some figures in the cycle with those found in three medieval treatises: the Introductio in Astrologiam, in the fourteenth-century transcription of a manuscript derived from Albumasar and attributed to Zaparo Fendulo; a thirteenth-century manuscript coming from the court of Alfonso X; and the edition, printed in 1488, of the Astrolabium Planum of Pietro d'Abano.
In examining some of the analogies, we see that the position of Cassiopeia, as it appears in the cycle, is the same in the first decade of the treatise by Zapari Fenduli, and at the seventh degree in both the rota of Alfonso X and the Astrolabium Planum of Pietro d'Abano. Moreover, the position of the image representing a fight between two dogs is the same at the twentieth degree of the Alfonsine rota and in the Astrolabium Planum of Pietro d'Abano.
For the Paduan astrological cycle, in addition to the analogous positions seen in these two examples, some iconographic models have also been found in medieval astrological texts.
In the case of the Constellation of Cancer, the figure of the Centaur depicted in the Paduan cycle, finds evident figurative references in the matching image of the constellation in both the Liber by Michael Scotus dating from the early 13th century and the treatise of Zaparo Fendulo.
As regards the representation of the Ship as well, we find clear figurative references in both the Astrolabium Planum and the treatise compiled at the court of Alfonso X.
Moving along the ecliptic and passing through the constellation of Cancer and that of Leo, we find interesting formal analogies between the representation of Hydra in the Paduan cycle and that of the above-mentioned astrological treatises. Particularly interesting is the contemporary presence of Hydra and Krater in both the frescoes of the Salone and the treatise of Michael Scotus.