The artist was inspired by actual buildings which he saw around him in Rome in the 17th century.
For example, the circular structure at the left is based on Bramante's Tempietto di San Pietro, and the palace next to it is related to the Palazzo Cancellaria.
The end result is however imaginary: invented classical buildings drawn together into a harmonious composition.
The vertical lines of pillars are carefully placed so that they balance and echo the masts of the ships in port.
An improbably large tree on the right is used as a counterweight to the buildings on the left.
Both direct our eyes towards the focal point of the picture, the rising sun.
