To complete the defensive apparatus of the Apostolic Palace, shortly after his election Alexander VI ordered the construction of the Borgia Tower (1492-94), which enclosed two rooms intended for service functions, identical in their architectural and decorative plan, produced by the workshop.
The female figures that lend their name to the room are silhouetted against the blue background, alternated with the Prophets, in accordance with an iconography of medieval origin, widespread in the fifteenth century. The Sibyls and Prophets are identified by the fluttering scrolls they hold in their hands, on which there are also the verses of the respective predictions and prophesies, pre-announcing the coming of Christ and showing how, in the common awaiting of the Messiah, the classical pagan world may be linked with the Christian world of the people of Israel. Starting from the door, the following couples are depicted: Isaiah-Hellespontine Sibyl, Micah-Tiburtine Sibyl, Ezekiel-Cimmerian Sibyl, Jeremiah-Phrygian Sibyl, Hosea-Delphic Sibyl, Daniel-Eritrean Sibyl, Haggai-Cumaean Sibyl, Amos-European Sibyl, Jeremiah-Agrippine Sibyl, Baruch-Samian Sibyl, Zechariah-Persian Sibyl, Obadiah-Libyan Sibyl.
In the octagonal tiles of the intermediate panels the seven major planets are depicted, represented in the sky as divinities born triumphantly on a chariot pulled by allegorical animals with the related sign of the zodiac. The human, social and professional categories subject to their influence on earth are shown: Saturn and the works of charity; Jove and the hunters; Venus (note the anomaly of the chariot drawn by bulls alluding to the Borgian coat of arms, rather than the traditional doves) and love; Apollo and governors; Mars and warriors; Mercury and merchants; Luna and fishermen; and finally, in the last panel, a number of astronomers and the armillary sphere, symbol of Astrology, a subject of great interest to the patron of the work.