Between December 1750 and November 1753, Tiepolo was commissioned with decorating the Prince-Bishop's newly build palace, the Residence. On the ceiling of the staircase, an unsuported trough-vault, Tiepolo painted a fresco depicting allegories of Apollo and the four continents. With a surface area of over 600 m², it is the largest fresco in the world and often considered his greatest achievement. An earlier draft that would have divided the vault into multiple frames depicting historical scenes, was discarded in favour of the present design. It is generally believed that this oil painting served as a preparatory sketch for the ceiling fresco which was presented to the Prince-Bishop on April 20, 1752.
However, the composition of the oil sketch differs from the final work. It has been suggested that Tiepolo had to shift the deities which represent the planets in order to make room for the portrait-medallion which is not present in the earlier draft. Lauding the Prince-Bishop as a patron of arts and culture, it had to be placed above his home continent, Europe.
