The idea of architecture as a living organism, already intuited by Filarete, does not limit itself to analogies with the human body: it surpasses them, transforming the city into an organism endowed with rhythm, metabolism, and breath. In his Treatise on Architecture (1461–1464), the building does not imitate human form but the vital process itself, accepting growth and physiological decay as expressions of the cosmic law that governs every living structure.Unlike Alberti, who seeks eternity in the solidity and permanence of architectural matter, Filarete imagines materials that age like skin, surfaces that mutate, urban tissues that require care. Maintenance becomes a therapeutic gesture rather than a repair: an act of continuity between the human body and the urban body.Gates, windows, water channels, and squares become the organs through which the city breathes. Streets flow like veins, squares pulse like hearts, and the entire urban organism synchronizes with the cosmic cycle. The astronomical orientation of the cardinal gates regulates the city’s respiration, aligning it with the movement of the sun: an urbanism that is not merely technical but a cosmic liturgy.With Filarete, the illusion of geometric immortality—the humanistic aspiration to eternal form—begins to fracture. The city no longer belongs to its users but to the souls that animate it, to the vital flows that traverse it. It becomes a place of mediation between the human cycle and the universal cycle, an organism that lives, changes, falls ill, and heals.Today, in the face of ecological crisis and the fragility of contemporary metropolises, Filarete’s lesson appears strikingly current: it reminds us that architecture is not an object but a time, a process, a shared breath between human beings, the earth, and the sky.