The basic layout of the city is an eight-point star, created by overlaying two squares so that all the corners were equidistant. This shape is then inscribed within a perfect circular moat. This shape is iconographic and probably ties to Filarete’s interest in magic and astrology. Consistent with "Quattrocento" or fifteenth century notions concerning the talismanic power of geometry and the crucial importance of astrology, Filarete provides, in addition to pragmatic advice on materials, construction, and fortifications, notes on how to propitiate celestial harmony within Sforzinda. His architectonical drawings and even more his allegorical drawings traced on the margins of the Codex Magliabechianus – such as the Allegory of Vertue and the Allegory of the Reason and Will – Filarete shows a remarkable possession of classical sources, maybe known also through the advice of his friend Francesco Filelfo da Tolentino, the main humanist then at the court of Milan.