Santucci's armillary sphere is a Ptolemaic armillary sphere at the Museo Galileo in Florence, the largest existing in the world. 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, and it also displays territories that were still relatively little known at the time.