Giovanni de' Dondi (1318-1389) was the second in a line of Italian clockmakers. His father, Jacopo de' Dondi (1298-1355), designed a clock for the Palazzo del Capitanio at Padua. In 1359 or 1352, Giovanni became a profesor of medicine at the University of Padua; several years later he was appointed to that university's four faculties of medicine, logic, philosophy, and astrology. He taught astronomy at the University of Padua, later lecturing on medicine in Florence, Italy. He also served as ambassador to Venice, Italy, and held several other political offices.

Dondi is remembered chiefly for his design and construction of an astronomical clock known as an astrarium. The astrarium (also referred to in contemporary accounts as a "planetarium" or a "clock") as it was called, took 16 years to complete. The astrarium connected the Ptolemaic model of the universe with contemporary horological knowledge. It also set a model for the construction of astronomical clocks on European buildings.

At the astrarium's unveiling in 1364, it proved to be one of the most elaborate astronomical devices yet created. The mechanism was set upon a two-part heptagonal framework. The top frame had seven dials to plot the movements of the sun and moon, as well as the planets Mercury, Venus, Mars, Jupiter, and Saturn--the only known planets in the fourteenth century. The bottom frame comprised a 24-hour dial, upon which were recorded ecclesiastical feasts as well as the lunar nodes (used to compute eclipses). At either side of this dial, the winter and summer solstices were recorded in keeping with the Julian calendar.

Dondi also provided a detailed treatise describing the device's workings, now considered by historians as one of the earliest recorded descriptions of any clock. Twenty years after the astrarium's completion, it was purchased by Duke Gran Galazzo Visconti, who housed it in his library at Pavia. The astrarium was prized as one of the most remarkable and beautiful artifaces of its time and was said to have been studied by Leonardo da Vinci, Regiomontanus, and Petrarch. The clock changed hands several times before falling into the possession of Charles V in 1529 or 1530, when it was considered beyond repair and was retired.

Modern clockmakers constructed replicas of the astrarium by following the design in Dondi's treatise. One of these replicas resides in the Museum of History and Technology in Washington, D.C.