Roman architecture – arches, concrete and domes

Roman architecture, from around 200 BC to the 4th century AD, built on the Greek orders but added the arch, the vault, the dome and concrete. This made it possible to build large indoor spaces, bridges, aqueducts and arenas. The Pantheon and the Colosseum in Rome are the best-known examples.

Facts

The arch and concrete

The Greeks built with columns and beams, but the Romans exploited the arch to the full. An arch of wedge-shaped stones carries the weight down into the piers and can span much further than a stone beam. Set arches in a row and you get an arcade, extend an arch and you get a barrel vault, and let two barrel vaults cross and you get a groin vault.

The other great invention was Roman concrete, opus caementicium. Lime mortar mixed with volcanic ash, pozzolana, and crushed stone gave a material that set even under water and could be cast into almost any shape. On the outside the concrete was often faced with brick, marble or render. Read more about arches and vaults.

The Pantheon

The Pantheon in Rome was rebuilt in its present form under the emperor Hadrian in the 2nd century AD. Behind a temple front with Corinthian columns lies a round hall covered by a dome just over 43 metres in diameter, equal to the height of the room, so that a sphere would fit exactly inside.

The dome is cast in concrete that becomes lighter towards the top, with heavier aggregate at the bottom and light pumice at the top. In the middle there is an opening, the oculus, which is the room's only source of light. The Pantheon's dome is still the largest of unreinforced concrete in the world, and the building has been a model for countless churches, museums and libraries.

The Colosseum and the public buildings

The Colosseum was inaugurated in AD 80 and could hold around 50,000 spectators. Its façade consists of three storeys of arcades with half-columns in different orders and a fourth storey with pilasters. Beneath the arena there were passages, cages and lifts for animals and gladiators.

The Romans built a range of new types of public building. The basilica was a large hall for trade and the administration of justice, which later became the model for Christian churches. The baths, such as the Baths of Caracalla, were bathing complexes with hot and cold baths beneath huge vaults. The Arch of Constantine and Trajan's Column celebrated the emperors' victories.

Engineering

The aqueducts carried water to the cities with an even gradient over long distances. The Pont du Gard in southern France, from the 1st century AD, is around 49 metres high in three tiers of arches, and the aqueduct of Segovia in Spain is built of dressed granite blocks without mortar.

Just as important were roads, bridges, harbours and town plans. Many European cities still keep their Roman grid of streets. The Porta Nigra in Trier is a well-preserved city gate from the 2nd century. The Romans built to last, and it shows.

The legacy of Rome

Vitruvius wrote that a building should have three qualities: durability, utility and beauty. His book was rediscovered in the Renaissance, and ever since Roman architecture has been a constant source. Renaissance domes, Baroque churches, Neoclassical museums and 19th-century railway stations all build on Roman models.

In Sweden too Roman forms are everywhere: temple fronts on churches and museums, domes and triumphal arches. Read more about the Roman style, about the classical orders and in the guides to Renaissance and Neoclassical architecture.

How to recognise it

Exercise

Which material made it possible to build the Pantheon's huge dome?