Architecture
Vitruvius's 10-volume work, De architectura, published around 35 BC, brings together a massive collection of information on architecture and related subjects. He provides detailed information on building materials and techniques, covering everything from baths, temples and theatres (for which he devises schemes to ensure the best possible acoustics) to siege engines, sewers, aqueducts and prisons. This is the most comprehensive architectural manual to survive from ancient times. No detail is spared: there is even a book dealing with interior design.

The Pantheon at Rome, completed in AD 126, is one of the greatest of Roman construction achievements. The building, which took eight years to build, takes the form of a huge circular hall, topped by a dome that is 42 metres (138 feet) in diameter – bigger than that of St Peter's in the modern-day Vatican. Two techniques make it possible: the arch and concrete, which are the keys to Roman construction techniques.

Stone quarries
The Romans quarry stone on a massive scale, using slave labour to carry out work that is both arduous and highly dangerous. The quarries at Syracuse, for example, which were opened by the Greeks, continue in use through the Roman period. It is estimated that some 40 million cubic metres of stone are quarried here during ancient times. As well as cut stone, the quarries also provide supplies of broken stone and rubble for use in concrete.

Different types of stone are used for different purposes. As Vitruvius writes:

'The stone in quarries is found to be of different and unlike qualities. In some, it is soft: for example, in the environs of Rome, at the quarries of Grotta Rossa, Palla, Fidenae, and of the Alban hills. In others, it is medium, as at Tivoli, Amirternum, and Mount Soracte and in quarries of this sort. In still others, it is hard, as in lava quarries. There are also numerous other kinds: for instance, in Campania, red and black tufas; in Umbria, Picenum, and Venetia, white tufa which can be cut with a toothed saw, like wood.'

Some of the highest-quality stone is Luna marble, named after the quarries near Luna (modern-day Carrara) in north-west Italy. This fine-grained, white stone is initially quarried in the 1st century BC, and Augustus – who boasts that he finds Rome made of clay and leaves it in marble – makes extensive use of it for his building projects. It is also popular with sculptors and will be used in later years by Michelangelo.

Industrial production
Long before the Industrial Revolution, the Romans are producing certain goods on an industrial scale. Pottery, in particular, is produced in massive quantities in large workshops, which then export their products throughout the empire and beyond. In the 1st and 2nd centuries AD, for example, many millions of pieces of fine, red- glazed Samian ware are produced in factories in Gaul and Italy. Mostly platters, bowls and drinking cups, their design allows for easy stacking. A crate of this pottery, still unpacked, had just been delivered to Pompeii from Gaul when the town is buried by the eruption of Vesuvius.

Glass
Although glass has been made for hundreds of years, the Romans have perfected new techniques that have turned it from a luxury into something that is used quite widely. In particular, through glass-blowing, first devised in the 1st century BC, glass can be blown into moulds, making possible the mass production of glass bottles, flasks, jars and beakers. Some of these are highly decorated.

One of the most beautiful blown-glass vessels in the entire empire is the Portland Vase. It has been made by first blowing a layer of white glass into a mould, and then a thicker layer of blue glass over the top of that. The white glass was then cut away to leave a delicately engraved scene of Roman figures and foliage, picked out in white on the blue background.

Metalwork
The Romans are masters in the use of all kinds of metal: gold, silver, lead, copper, tin, zinc, iron, bronze. Indeed, some parts of the empire – such as in Asia Minor – are important to Rome principally because of their supplies of precious metals. Working in the mines, a task carried out almost entirely by slaves, is one of the worst possible occupations, with appalling conditions and terrible death rates. But the metal that they produce is central to the success of the empire. Whether it is iron used for the weapons and armour of the legions, or gold and silver for coins, the empire depends on it for its very survival.

The Romans are also great users of metal for aesthetic purposes. Small workshops and itinerant metalworkers produce huge quantities of jewellery and other decorative items. Some towns also come to depend for prosperity on the metal-working skills of their inhabitants. For example, one of the reasons why the Christian missionary, Paul, gets such a rough ride when he visits Ephesus is that his preaching is seen as a threat to the cult of Diana, around which the townsfolk have grown wealthy by selling silver trinkets to pilgrims to her temple.

Woodworking
The techniques and tools that Roman carpenters employ will be familiar to anyone working with wood today. The Romans use saws, drills, axes, adzes and chisels, and have a good understanding of the different kinds of joints and which ones are best for which purposes. They don't have screws, but they do use nails and wooden pegs. The quality of their workmanship stands out from that of other peoples around this time.

Their saddle, dovetail and tenon joints are all cut with a saw, while the mortices are drilled out with a bow drill. Bow drills are also used to make dowel holes – the holes for wooden pegs – on draw-tongue joints. The rough-cut joints are finished with a chisel.

All roads lead to Rome
There are at least 50,000 miles of well-surfaced roads in the Roman empire, and they are built as straight as possible. The Roman surveyors – agrimensores – are not only extremely accurate in their work; they also have no need to worry about who owns or uses the land along the way. As conquerors, they can simply choose the most direct route from A to B.

The road system is an essential part of the Roman economy. In the countryside, this is based around villas, whose estates produce far more food than they need for their own purposes and provide supplies to the army as well as to the growing urban populations. The roads also make possible the mass production and trade of pottery and other goods.

The cursus publicus, or imperial postal system, depends on the roads, too, to take official notices and correspondence around the country. Using relays of horses, it is possible for a messenger to travel 100 miles a day when his business is urgent enough. Stables and lodging houses are positioned at regular intervals on major routes.

Most Roman roads are built – in the first place, at least – by soldiers. Roman armies travel with their own surveyors and engineers and whatever equipment they need for construction work along the way (including their nightly camps, which they erect themselves at the end of each day's march). Later improvement and maintenance work is often carried out by prisoners or forced labour. The most famous Roman road of all, the Via Appia, from Rome to Capua (and later Brindisium, modern-day Brindisi), is built in 312 BC; its function initially seems to have been entirely military.

Local conditions, including the availability of suitable construction materials and the time available to complete the job, dictate the details of road construction. However, the basic principles are constant throughout the empire.

The road usually takes the form of an embankment – or agger – raised above the level of the surrounding land, with drainage ditches on either side. The embankment is cambered for drainage and can be 10 metres (33 feet) or more wide. It is rarely less than about 4 metres (13 feet) in width, so as to allow room for two wheeled vehicles to pass.

The road itself is built up in a series of layers, comprising a foundation of larger rocks, followed by smaller stones, gravel and sand laid down successively and pressed firmly into place. A cobbled surface is commonplace in towns or areas of heavy use, but often it is just firmly compacted gravel.

Roman roads are so effective that, in the later empire, they actually become a liability because invading forces can travel along them just as quickly as the Roman armies. Indeed, some roads are deliberately blocked during the last days of the empire.

'The first task here is to trace furrows, ripping up the maze of paths, and then excavate a deep trench in the ground. The second comprises refilling the trench with other material to make a foundation for the road build-up. The ground must not give way, nor must the bedrock or base be at all unreliable when the paving stones are trodden. Next the road metalling is held in place on both sides by kerbing and numerous wedges.

'How numerous the squads working together! Some are cutting down woodland and clearing the higher ground, others are using tools to smooth outcrops of rock and plane great beams. There are those binding stones and consolidating the material with burnt lime and volcanic tufa. Others again are working hard to dry up hollows that keep filling with water or are diverting the smaller streams.'
Statius (AD 61-96), describing the building of a new road near Rome

Bridges
The Romans are the first civilisation to develop real expertise in bridge building, both in timber and stone. The earliest known named bridge is the Pons Sublicus, a timber bridge constructed in Rome during the 6th century BC. The stone-built Pons Fabricius, one of eight ancient bridges crossing the river Tiber, built in 62 BC, is still standing 2,000 years later. The emperor Trajan's bridge across the Danube, built to facilitate the invasion of Dacia, doesn't last that long, but is a phenomenal engineering achievement.

Roman bridge building follows a set pattern: survey and design; quarrying and cutting the stones; constructing the abutments; building the foundations and piers; completing the arches; and, when all that is finished, adding any decorative features and inscriptions.

Tunnels
Hills and mountains are no obstacle for Roman engineers. They cut roads into the sides of mountains, and when no other route is available, they will even dig tunnels.

These do not always go according to plan, however. In the 2nd century AD, the Roman military engineer Nonius Datus is sent to the town of Saldae, in north Africa, to solve a problem resulting from two groups of workmen tunnelling through a hill from opposite directions. Datus calculates that the two tunnels must have passed each other beneath the hill. He solves the problem by digging a new tunnel sideways to connect the two.

Aqueducts and reservoirs
The Pont du Gard, which supplies Nemausus (Nimes) with water, is built to serve a colony of former soldiers. Elsewhere, the Romans think nothing of building aqueducts over long distances to supply fresh water to the towns and cities of empire.

Lighthouses
The Romans build and maintain lighthouses as an aid to shipping in various parts of the empire. There are two at Dover, for example, one of which – 24 metres (79 feet) in height – is still standing in modern times. Fuel for the fire on top is raised by a system of winches, cranes and pulleys.

Other important Roman lighthouses include: La Coruña, the 54m (177ft) high 'Tower of Hercules' in north-west Spain, which is still in use in the 21st century; the emperor Claudius's construction at Rome's port of Ostia, which is built on the sunken hull of a ship that brought an obelisk from Egypt; and the famous marble Pharos of Alexandria, which is at least 85m (279ft) tall and continues in use until its destruction in a 13th- century earthquake.

War
Roman technology is driven by the needs of its armies and war. Every legion has its own surveyors and engineers, and great expertise and practical experience in the technology of war. It harnesses the best iron-making technologies of the day to arm and equip its soldiers, even devising a form of steel especially for swords and other weapons. Its ballistas and siege engines are the most powerful and sophisticated in the ancient world.

Proof that not even the most formidable fortresses are defence against Roman innovation and know-how is to be found at the Palestinian desert outpost of Masada. Here, a desperate band of Jewish rebels is eventually defeated when the Romans build an enormous ramp to breach their defences on top of a rocky outcrop surrounded by sheer cliffs.

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