The Roman Republic began in 509 BC, marking the start of a distinct architectural journey that would eventually span centuries. Before this date, Etruscan builders dominated the Italian landscape with their own unique styles and techniques. Greek influence arrived through Magna Graecia, the southern Italian colonies, and indirectly via Etruscan intermediaries. The sack of Corinth in 146 BCE brought Greek artworks directly to Rome, providing models for local architects and artists. This influx transformed Roman building practices from simple trabeated structures based on columns and lintels into something far more complex. By the early Imperial period around 27 BC, Romans had combined these foreign elements into a new identity. They moved away from relying solely on columns to support heavy beams, instead developing massive walls punctuated by arches. The classical orders became largely decorative rather than structural, except within colonnades. Stylistic innovations included the Tuscan order, a shortened variant of the Doric style, and the Composite order, which blended floral Corinthian details with Ionic scrolls. Most surviving buildings date from after 100 AD, when the Empire reached its peak construction phase. The period between 40 BC and 230 AD saw the greatest achievements before the Crisis of the Third Century reduced central government resources.
The Concrete Revolution
Innovation began in the third or second century BC with the development of Roman concrete known as opus caementicium. This material quickly supplanted brick as the primary building substance, allowing for daring new forms. Ancient builders mixed lime mortar, aggregate, pozzolana, water, and stones to create a mixture stronger than any previously used. The first use occurred in the town of Cosa sometime after 273 BC. Workers placed these ingredients inside wooden frames where they hardened and bonded to facing stones or bricks. The aggregates often amounted to rubble much larger than modern concrete uses. When the wooden frames were removed, the resulting wall was very strong with a rough surface that could be smoothed or faced with stucco. This freedom allowed architects to build great pillars supporting broad arches and domes rather than dense lines of columns suspending flat architraves. The invention enabled the creation of vaulted ceilings without crossbeams and made possible large covered public spaces like baths and basilicas. Hadrian's Pantheon stands as the most famous example of this revolutionary technique. These developments remained unsurpassed until the introduction of structural steel frames in the late nineteenth century. Concrete construction proved more flexible and less costly than solid stone buildings while materials remained readily available.