How did Andrea Mantegna make the flat ceiling of the Camera degli Sposi appear concave?

Andrea Mantegna achieved the illusion of a concave ceiling in the Camera degli Sposi by employing a system of highly realistic painted architectural elements across the room's surfaces.1

By integrating these fictive architectural features with the room's actual structure, he transformed the flat ceiling into an elegant, open-air pavilion. Central to this effect is a painted oculus—a circular opening to the sky—featuring putti and women depicted in a technique known as sotto in su, which uses extreme foreshortening to make figures appear as though they are suspended in the air above the viewer.12

This total spatial illusion relies on a strong vertical axis that anchors the spectator to a single, specific point in the center of the room. From this vantage point, the observer's physical space seamlessly blends with the painted environment, creating the convincing impression that the flat ceiling is curving upward into an open sky.1