Exploitation of the arch and use of concrete characterize the great public buildings of the Roman era: temples (Pantheon), amphitheatres (Colosseum), baths (Caracalla), theatres, roads, bridges and aqueducts.


The Romans did not invent the arch, but their development of it enabled them fully to exploit their penchant for resolving improbable situations by vast expense of labour.

Orders of architecture

(Illustration by John Pittaway from Picture Reference Ancient Romans, Brockhampton Press 1970)

The Romans took from the Greeks the three orders of architecture, Doric, Ionic, and Corinthian, based on different forms of column and the capital which surmounted it, and added a hybrid of their own, known as Composite. That they could indulge their architectural ambitions was due to the indubitably Roman invention of concrete. Its basis was pozzolana, a chocolate-coloured volcanic earth originally found near the Greek settlement of Puteoli, and subsequently discovered in vast quantities around Rome.

Wall construction

(From Helen and Richard Leacroft, The Buildings of Ancient Rome, Brockhampton Press 1969)

Pozzolana was used to make mortar and also, when mixed with lime and strengthening materials such as chips of rock and broken brick, concrete. Judicious use of bricks and concrete together enabled massive, permanent structures to be built. Once concrete had taken the place of rubble as the filling of a wall, it was possible to use irregularly shaped stones as facing, with courses of brick to bind it. This was known as opus incertum. With opus reticulatum square-based pyramids of stone were inserted with the heads facing inwards. A further development was opus testaceum, in which triangular baked bricks were used.

Opus reticulatum

Opus reticulatum, Pompeii. (VRoma: Lisanne Marshall)

Their command of materials and techniques enabled the Romans to construct circular temples, the most spectacular of which is the Pantheon, rebuilt between AD 120 and 124 in the reign of the emperor Hadrian.


Cutaway drawing of the Pantheon, showing the inside of the building. The hemispherical dome is 43.28 metres in diameter, and if completed would exactly touch the ground. The only light falls through an eight-metre wide gap in the top (see note in right hand column). (From Helen and Richard Leacroft, The Buildings of Ancient Rome, Brockhampton Press 1969)

The remains of Roman buildings are a guide to the enormous areas which some of them covered. The main block of the baths of Caracalla to the south-east of the city, which could accommodate 1600 bathers at a time, was 216 by 112 metres.The baths of Diocletian, completed in about AD 305, could accommodate twice as many. Roman architects were less concerned with external appearances than with the creation of inner space, which the dome, where it was employed, enhanced.

Model of Rome

Model of central Rome in the fourth century AD, from the south. (VRoma: EUR (Rome), Museum of Roman Civilization: Barbara McManus)

In their construction of public baths as luxury-cum-cultural leisure and sports centres, the Romans combined their passion for opulence with their flair for hydraulics.

Cutaway model of Roman baths.

Cutaway model of a typical Roman baths. (Saalberg Museum: Barbara McManus)

For their theatres, the Romans followed the Greek plan of tiers of seats in a semi-circle facing the stage, but whereas the Greeks tended to take advantage of natural slopes on which to erect the seats, Roman theatres were usually built on level ground. The first stone theatre in Rome was opened in 55 BC.

Theatre diagram

The whole theatre could be covered by the velarium, a great canvas roof hung on masts to protect the audience from the sun. The public entered and left the auditorium through openings known as vomitoria, according to where their seats were. (From Helen and Richard Leacroft, The Buildings of Ancient Rome, Brockhampton Press 1969)

The Romans took their architectural techniques with them, wherever they settled. Solid evidence of the Romanization of their extensive empire still stands in parts of north Africa and the near east, and in what was the province of Gaul. The biggest cluster of remains outside Italy is in Provence, where Arles, Nîmes, and Orange can between them boast two amphitheatres, two theatres, a temple, and a triumphal arch.

maison carree

Maison Carrée, Nîmes, built probably in 16 BC, is the most complete remaining example of the temple architecture of the Augustan age. (VRoma: AICT)

The extension and retention of an empire required the construction of town walls. Roads and bridges were needed for speedy communications and the deployment of troops, and aqueducts to supply populations adequately with water. Towns on exposed ground could comparatively quickly be turned into fortresses by the raising of walls consisting of a base of large stone blocks, then a deep course of rubble faced with concrete, topped off with alternate layers of stone and tiles.

Hadrian's Wall

Hadrian’s Wall was built largely between AD 122 and 127 on the orders of the emperor Hadrian to facilitate the control of the frontier between Britain and the tribes to the north. Except for the period between about AD 143 and 165, when the Antonine Wall was in operation across the Clyde - Forth isthmus, Hadrian’s Wall marked the northernmost frontier of the empire. It ran 73 miles from coast to coast, following the natural crags in the terrain, and comprised a V-shaped ditch up to 5 metres deep and 12 metres wide, dug where necessary out of solid rock. Behind it was a wall 5 metres high and about 3 wide, with battlements on top. There were seventeen forts along its length, and every Roman mile a tower, between each pair of which were two fortified turrets. (VRoma: Susan Bonvallet)

The empire was held together by a network of roads, branching out from all the main towns and joining up with the quickest and safest sea routes. The building and upkeep of roads were the responsibility of the state, and military roads in the provinces were constructed by the army, with some additional forced labour from the local people.

Road construction.

Illustration by John Pittaway from Picture Reference Ancient Romans, Brockhampton Press 1970.

According to an “itinerary” compiled in the reign of Antoninus (AD 138 - 61), the extent of metalled or paved roads in Italy was approximately 14,000 miles; in Gaul 8750 miles; in Spain 7000 miles; in Britain (parts of which were still unknown) 2,800 miles; in Africa 8750 miles; in Asia 9500 miles. All were provided with milestones - there were 5 Roman feet to a passus (pace), and 1000 paces to a Roman mile (mille passus or mille passuum), which was thus 1.48 km or 0.925 of a mile.

arch of severus

Arch of Septimius Severus in the Forum, erected AD 203 to celebrate his victories over the Parthians and the Osroeni. (René Seindal)

A solitary triumphal arch can hardly give aesthetic satisfaction unless its proportions are in tune with its surroundings, and the Romans do not seem to have given much thought to that aspect. The true triumphal arches are thus those which support the bridges and aqueducts that have survived.


At Alcántara in Spain, six arches of unmortared blocks of granite, the two centre ones 55 metres above the water, carry the road across the river Tagus. The bridge was built in about AD 106, and an inscription in a temple nearby reads: “The celebrated Lacer built this bridge with supreme skill to endure through the ages to eternity.” (VRoma: Paula Chabot)

The arch enables wide spaces to be crossed by the use of the minimum of materials, thus relieving weight which would otherwise put an intolerable burden on the structure. To the countryman, the most astonishing manifestation of the civilization of Rome must have been the rows of arches, sometimes three tiers of them, which marched across the plains and gorges, bringing fresh water from the mountain springs and lakes in a covered channel gently down in an imperceptible gradient into the intricate mechanism which piped it through the towns. The Romans knew about the rule of dynamics that water always rises to the level of its source. They did use underground pipes, and where necessary tunnelled through hills which could not easily be skirted, but building materials and labour were cheap and readily available, whereas large-bore pipes were expensive and less reliable.

pont du gard

The Pont du Gard, 25 km west of Avignon, originally 275 metres long, carried water along a channel on top of three tiers of arches towering 50 metres above the river. (VRoma: AICT)


Reconstruction of the water channel of the Pont du Gard, first century AD. (From Helen and Richard Leacroft, The Buildings of Ancient Rome, Brockhampton Press 1969)

The most famous aqueduct in ancient times was the Claudian aqueduct, begun by Caligula and finished by Claudius. It had a channel 70 km long and started its final overhead descent to Rome 12 km out.

Aqua Claudia

In the model of Rome, the Claudian aqueduct (foreground) nears the end of its journey. It was one of eleven similar structures which brought water to the city. (VRoma: EUR (Rome), Museum of Roman Civilization: Barbara McManus)

The municipal water board which maintained the system consisted of 460 slaves whom Claudius took on to his personal staff, with a special commissioner in charge. In AD 97 Nerva appointed as inspector of aqueducts Sextus Julius Frontinus, a former governor of Britain. In an exhaustive report, Frontius estimated that over 1000 million litres of water a day came into Rome through the eight aqueducts which were then operational.


Model of Roman crane. (VRoma: Paula Chabot)


The orders of architecture.

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Cement & concrete

It wasn't until 1824 AD that an English bricklayer re-discovered this great ancient invention: if you mix clay and limestone and heat it to a high enough temperature the substances fuse. If that is then pulverized, you get a powder which, when mixed with water, sets as hard as rock.


The word, in Greek, means “all gods”, and the Pantheon is unusual in that it is dedicated to multiple gods, of whom statues of seven stood in recesses around the circular walls. The original temple was built in about 27 BC by Marcus Agrippa, son-in-law of Augustus, and was dedicated especially to Mars and to Venus, in the ears of the statue of whom hung earrings made from pieces of Cleopatra’s pearls. It burned down in AD 80.

Believe it or not:

In the year 28 BC, Augustus, by his own account, rebuilt 82 temples and repaired numerous others.
To entertain the crowds celebrating his quadruple triumph in 46 BC, Julius Caesar had a wooden amphitheatre constructed to his own design.
The Romans built amphitheatres wherever in the empire there were enough troops to justify them. The farthest north of which traces have been found is at Newstead in Scotland, for the entertainment of the permanent garrison of about 1000, between 2000 and 5000 at any one time temporarily encamped in the complex, and soldiers from smaller forts in the region.
Roman architects believed in creating vast inner space. The Church of Santa Maria degli Angeli in Rome was converted by Michelangelo in 1563 from just one hall of the baths of Diocletian.
By 13 BC there were three stone theatres in Rome, the smallest seating 7000 and the largest 14,000, compared with the 3000 capacity of the present Scala in Milan, the 2268 of the Royal Opera House, Covent Garden, London, and the 4000 of the new Metropolitan Opera House in New York. These figures are tiny, however, when compared with the 265,000 spectators at a time who watched the chariot races in the Circus Maximus, and the 87,000 at the games in the Colosseum.
Good roads enabled a special messenger in AD 69 to travel from Mainz to Rome via Rheims (over 1300 miles) in about nine days. In 46 BC, Julius Caesar travelled from Rome to southern Spain by carriage, a distance of about 1500 miles, in 27 days.