Officinae machinarum militarium
aedes : a dwelling of the gods, a sanctuary, a temple, a simple edifice, without division into smaller apartments, while templum is a large and splendid structure, consecrated by the augurs, and belonging to one or more dieties; but after the Augustan period aedes was used for temple
officina : a workshop, manufactory
officinae armorum : a manufactory of arms
machina : a machine, i.e., any artificial contrivance for performing work, an engine, fabric, frame, scaffolding, staging, easel, warlike engine, military machine
militarium : of the military
Volcanus (Vulcanus) : Vulcan, the fire-god, son of Jupiter and Juno
The military machine complex of the Aedes Vulcani, the Officinae Armorum, and the Officinae Machinarum Militarium, which Piranesi postions near the north end of the Equiria, is both literally and figuratively the star of the Equiria's overall military program. This group of buildings represents the manufacturing headquarter's of ancient Rome's armed forces. It is thus a center of civic pride as well as a tribute to Mars, and its placement along the Equiria is entirely fitting, even though the whole design is without historical or archeological substantiality.
Tafuri, a late 20th century Italian architectural historian, describes the Officinae machinarum militarium as a "clockwork mechanism, in which, however, there is an independence of the parts and a lack of interest in formal qualities." Unfortunately, he failed to recognized the overriding "martian" theme of Piranesi's Equiria design, and only scrutinized the geometry of the military factories. Even more disappointing is the fact that Tafuri did not seize upon the appropriateness of associating "clockwork" with factories. In Piranesi's defense, the spatial layout of the Officinae machinarum militarium and the Officinae Armorum is extremely connective because of the many door openings throughout the complex, a quality completely suitable for manufacturing and assembledge processes.
In the center of the Officinae machinarum militarium is the Aedes Vulcani, a small circular temple or shrine surrounded by a circular pool of water and dedicated to the god of fire. The Officinae machinarum militarium itself is a six pointed star shaped plan within a circular perimeter wall, with two small cruciform wings at either end. The Officinae Armorum is essentially four sets of linear celled buildings divided into pairs with a long pool building inbetween. Together, the three buildings comprise a bi-laterally symmetrical composition whose many openings create a complex of abundant connectivity.
On a purely figurative level, the complex's plan resembles a military insignia of honor.