In the first months of 1529, Michelangelo was nominated “general governor and procurator of the fortifications” and, in this role, the artist improved himself in the realization of several elaborate projects of fortifications. This sheet refers to a fortification system studied to protect the Porta al Prato of Ognissanti. Although the projects were never realized, for their own complexity, their existence states the Michelangelo’s extraordinary imagination also in the military stategy’s field.