Giovanni de' Dondi's astrarium
Working model; reconstruction by A. Segonds, E. Poulle, J.P. Verdet
Paris, Observatoire de Paris, inv. 404, anc. 20-36
De' Dondi's astrarium is the oldest planetarium that shows the movements of all the planets known in the Middle Ages (including the Sun and the Moon). A single weight-driven motor drives trains of gears that set the seven stars in motion. Each of their trajectories is visualised on a dial. Giovanni de' Dondi's manuscript (14th century) contains an extremely detailed plan of the astrarium, thanks to which it has been possible to build a faithful and fully functioning replica of the lost original of this extraordinary planetary clock, which was considered a mechanical miracle not only by de' Dondi's contemporaries but also by scholars of later generations.