The Roman people, of a more practical temperament than the Greeks, developed an eminently utilitarian architecture within the scope of their Empire. This was above all, an urban civilization, a network of cities dominated militarily; thus, the idea of military rule was the basis of Roman architecture, which always had a frame of reference in cities.
When the Romans built walls, aqueducts, roads, triumphal arches, etc, they only reinforced their imperial domain, putting architecture at their service. Its architecture thus had a clear political meaning.
They used a variety of materials -stone, concrete or mortar and brick- in their solid constructions.
-Stone: Sometimes they used irregular stones joined with mortar. It is the type of septum called opus incertum. Sometimes, they gave the stone the shape of a pyramid with a square base, which, when inserted into the wall, formed a kind of partition in a grid called opus reticulatum. But it is the ashlar rig, the opus quadratum, the most important. It is arranged according to the rope system (piece placed parallel to the wall) and across (piece perpendicular to the wall), alternately. Sometimes the ashlars presented the external face with a convexity that gave them a decorative appearance. It is called padded ashlar.
-Concrete: (opus cementerium) or cement, it was builtwith a mixture of water, sand, lime and pebbles, determining when it dries a solid, indestructible mass.
-Brick: (opus lateritium) consisted of large rectangular pieces of little thickness. The o pus mixtum, typical of the Lower Empire, consisted of arranging alternate layers of bricks and stone, with a harmonious color contrast.
If Greek architecture is architraved, that is, it solves the problem of the roof with horizontal solutions (architraves, lintels), Roman architecture is vaulted, since it uses the arch and the vault. For this reason, this one is much more complex than that one. The arch used is the semicircular or semicircular. As far as the vaults are concerned, they used the barrel and groined vaults, in addition to the dome.
They adopted the Greek orders, and introduced novelties:
-The Tuscan Order (variant of the Doric): It consists of a plinth and base with a thick torus, the shaft is smooth and with entasis. The capital, preceded by an astragalus (a tiny torus) and a ring, is formed by the equinus (a quarter round) and the abacus. This Doric-Tuscan order derives from Etruscan architecture.
-The Composite Order: Compromise between the Ionian and the Corinthian. The composite capital offered Corinthian-style acanthus leaves, but also has two rows of ovas and pearls, and large scrolls taken from the Ionic. At the same time, the entablatures are considerably enriched. The friezes used to be adorned with reliefs of garlands (leaves joined with ribbons, forming a voluminous band hung by theends) and bucráneos (ox skulls).
Fruit of Roman utilitarianism, the most significant part of its architecture will not be the temple (as in Greece), but civil constructions, public works with a practical purpose. Great constructions that we will find collected in De architectura, a 10-volume treatise compiled by Vitruvius towards the end of the 1st century BC