Begun on March 4, 1588, and completed on May 6, 1593, this large armillary sphere was built under the supervision of Antonio Santucci at the request of Ferdinand I de' Medici. The sphere represents the "universal machine" of the world according to the concepts developed by Aristotle and perfected by Ptolemy. The terrestrial globe is placed at the center. Surprisingly, it even displays territories that were still relatively little known at the time.

Restored in the nineteenth century by Ferdinando Meucci, the device is now incomplete and some of its parts are mismatched. The wooden parts of the sphere are elaborately painted and covered with fine gold leaf. The sphere rests on a stand with four sirens, heavily restored in the nineteenth century.

This model is similar to a smaller one built by Santucci in 1582 for King Philip II of Spain, now in the Escorial library. Provenance: Medici collections.