The armillary sphere is a scientific instrument used to display and study the motions of the celestial sphere in relation to the earth. It consists of a metal frame with graduated circles (the name derives from the Latin armilla, meaning a ring or bracelet). The central golden globe represents the Earth, while the rings which move around the central vertical axis indicate the position of the Tropics of Cancer and Capricorn, the apparent journey of the Sun, and the movement of the Moon. The horizontal fixed ring reproduces the horizon with the signs of the zodiac, the meridian and the hourly circle subdivided into 360 degrees.
This rare and precious object shows the state of the astronomical knowledge in the mid-sixteenth century, still based on a geocentric outlook. It is signed on the base by Gualterus Arsenius, member of a sixteenth-century Flemish family of engravers and makers of mathematical and geographical instruments, famous for their elegance and precision.