Rome as 'Part of the Heavens"? Leon Battista Alberti's Descriptio urbis Romae (ca. 1450) and Ptolemy 's Almagest.

The article examines Leon Battista Alberti's mid-15th-century treatise *Descriptio urbis Romae*, highlighting its innovative method for mapping Rome through instructions rather than illustrations, enabling accurate, scalable depictions based on plotting 175 coordinate points. It situates Alberti's work within the intellectual context of Ptolemy's *Geography* and *Almagest*, showing how Alberti fused geographical precision with astronomical concepts—such as circular coordinate systems and instruments akin to astrolabes—to render Rome as a "part of the heavens" (pars caeli). Unlike traditional chorographical city views, Alberti's map employs a polar coordinate system centered on the Capitoline Hill, evoking celestial star charts and reflecting Renaissance intersections of astronomy, astrology, and geography. The article also discusses Alberti's connections with contemporary astronomers like Johannes Regiomontanus, underscoring Alberti's role as an astronomer-cartographer who translated Rome's terrestrial topography into a cosmologically symbolic image.