Since antiquity, astronomers have studied the movement of the stars, striving to reproduce the appearance of the heavens by means of suitable models. One of the oldest solutions to this problem is globes, in which the constellations are shown on the surface of a metal sphere engraved with the main celestial circles: the horizon, the meridian, the equator, the tropics, and the ecliptic. In armillary spheres, the relationships between these circles and the planetary movements are displayed through a combination of concentric rings revolving around the axis of the sphere.