Neptune, the Roman god of the sea, grasps his trident while resting one foot on the scaly head of a dolphin. He stands on a pedestal against a pilaster, the base of which is mainly defined by the dolphin's body. On each side are the hastily drawn lines of a vertical piece of architecture, while farther to the right are the dark shadows of his arms and trident.
Giulio Campi probably produced this sketch as a preparatory study for the decoration of one of the triumphal arches erected in Cremona on the occasion of Emperor Charles V's entry into the city on August 18, 1541. Decorated with statues and representations of his famous deeds and insignia, these arches marked the ruler's route through the city gates to his lodgings. The number of pentimenti in this rapidly drawn work suggests to scholars that Campi completed the drawing in some haste, probably working under a tight deadline. For example, he produced two further alternatives for the position of the head, both in profile and tilted farther back, but he did not bother to reinforce either in darker chalk.