Building an Empire and a Legacy: Roman Engineering

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Building an Empire and a Legacy: Roman Engineering

Overview

The engineers of ancient Rome designed and constructed many projects to serve the needs of an urban and an imperial nation. With their use of the semicircular arch, the barrel vault, and hydraulic cement, they transformed architecture and construction in the ancient world. The results were impressive in scale and practicality and influential in their shaping of a timeless architectural style.

Background

Roman civil engineers and architects created a series of structures intended to address the multifarious needs of Roman society. From the religious to the secular, from the recreational to the utilitarian, and from the military to the domestic, they engaged in a wide range of projects. Perfecting techniques inherited from earlier cultures such as Egypt and Greece, they added their own special contributions that came to mark a structure or design as Roman. Relying on a variety of materials such as clay, brick and mortar, limestone, marble, and tufa (a form of volcanic mud), they addressed the needs of an urban-centered society that expanded its reach and influence into the known Western world.

Among those many needs were the requirements of a hydraulic culture in which supplying and controlling water dominated the activity of the societies. The Romans responded with aqueducts, tunnels, siphons, dams, and sewers. They built massive aqueduct systems of brick and stone that brought water from the mountains into urban centers. Using the gravity feed principle allowed Roman engineers to transfer water in some aqueduct systems for as much as 40 to 50 miles (64 to 80 km).

Using arches to span valleys, these engineers produced elegant and effective water channels that delivered a volume of water equivalent to the basic needs of many twentieth-century European cities. For example, the Pont du Gard, in the south of France, spanned the river Gard with a three-tiered arch bridge reaching a height of 160 feet (49 m) and brought water to the city of Nimes. To supplement the expensive aqueduct system, Roman builders also used tunnels and siphons to move water as well. As a complement to the aqueduct system, dams composed of rubble, brick, and stone along with reservoirs provided a store of water for domestic use or to power water mills, especially those for grinding grain. Romans also used their hydraulic engineering skills to supply water to various public baths, to provide water for domestic needs, and to remove wastes through an extensive sewer system.

To meet the many challenges of their urban needs, the Romans relied greatly on a waterproof material, hydraulic cement, available to them because they had access to vast quantities of pozzolana sand or ash generated by volcanoes. This special substance gave them a material that could be used under water for bridge piers, was fire-resistant, and could withstand the effects of the weather. It also added to the durability of mortar used to secure bricks or stone in place in many structures. The full utilization of this material allowed Roman engineers to construct durable buildings and bridges and other projects on a massive scale.

The extended arch or barrel vault gave the Romans a new technique for enclosing space. In buildings such as theaters, amphitheaters, circuses, public baths, and basilicas, this new architectural element appeared repeatedly. The arch itself became a defining element in various stadia such as the Colosseum in Rome, functioning as entrances and exits and in tiered form to add to the structure's height. Used as a vault, it defined passageways, ceilings, and graceful interiors that created vastly larger spans than had been present in the ancient world. The Colosseum itself, with its many arched openings, gave the impression of vast open interior space when, in fact, a massive hidden structure provided the support for this interior, which would hold between 45,000 and 50,000 spectators. Eighty arches on the exterior wall allowed for easy entry and exit and provided ready access to the whole building. This successful design was also combined with the post and lintel style of many columns in symmetrical array so that the arch and vault created a durable classical style of architecture that permeated the Roman world.

The arch and barrel vault were combined in one of the most impressive basilicas in ancient Rome, the Basilica of Maxentius. With its 260-foot (79-m) length and 80-foot (24-m) vaults, this structure dominated the Roman Forum. Three main vaults with coffered ceilings, a common decorative feature of Roman interiors, dominated the building. The result was the largest hall built in antiquity.

Elaborating on the arch and vault, Roman architects also pioneered the use of the circular dome. Unlike the Greeks, the Romans built enclosed space and focused on interiors. The most spectacular result of dome construction was the Pantheon in Rome, a temple whose dome, complete with a 25-foot-wide (7.6-m) oculus, was 142 feet (43 m) in both diameter and height, the largest dome in the West until St. Peter's was built in Rome in the sixteenth century. Like many other Roman interior spaces, the dome had a coffered ceiling with the simple geometry of nested squares; the resulting rotunda interior created an overwhelming sense of uninterrupted space, of a dome the floated in space, in a simple design unequalled in the ancient world.

An outgrowth of Roman experience with the arch, the Pantheon's dome was constructed as a series of linked segmental arches or vaults, a technique widely used by Roman engineers. Step rings, a solid foundation, and the building itself support this very large heavy dome, which has survived for centuries and, as one of several extant original Roman buildings, remains a testament to Roman engineering ingenuity and as an example of the best of Rome's concrete vaulted architecture.

The Romans used their skill as civil engineers on roads as well as buildings. Treating a road surface like a wall buried in the earth, they created a series of primary and secondary roads that together covered almost 200,000 miles (321,900 km). Built to last for a century, these roads shared the characteristics of a straight path, gradual gradients, curved surfaces for water runoff, curbs, and gutters. Often 6 feet (1.8 m) thick, the primary roads consisted of a series of rock, stone, and gravel layers covered with paving stones. Because they were a means of moving men and materiel as well as an effective means of communication, they were as essential to the successful operation of the nation and empire as the methods of water control and distribution so characteristic of Roman achievements.

This extensive road system benefited from Roman bridge-building techniques. The semicircular arch was the basic motif of Roman bridges, with a range of graceful spans from a single stone arch to multiple arches covering larger areas. The use of hydraulic cement allowed the builders to erect durable stone bridges that have stood and been used for centuries. Dispersed throughout the Roman world, these bridges became hallmarks of the classical architectural style as elegant ways to span space.

As a major force in the classical world, Rome required buildings and structures to serve its military needs. Massive stone walls, forts, and watch towers emerged over a period of years to protect and expand the Roman Empire. In an era when stone walls surrounded towns and cities in order to protect those within from attack, the Romans built impressive stone barriers, often with several gates and towers, to control access to urban centers. These defensive perimeters evolved into an elaborate system of walls, watch towers, forts, castles, and turrets that, in some cases, successfully served as defensive perimeters for more than 1,000 years.

Another Roman architectural legacy is the triumphal arch. Varying in style from one to four archways, these monuments celebrated leaders of the empire, military figures or victories, towns or cities, and various religious figures. As decorative features in an urban setting, these arches often served as a focal point in a city center or in defining a major gateway.

Roman domestic architecture produced a spectrum of housing from luxury villas to apartment houses in cities. Usually constructed of brick or stone, houses often were built around an atrium and, if space was available, included a garden. Rooms were arranged so that inhabitants could move from place to place within to seek or to avoid the sun depending on the climate or the season. Various dwellings also incorporated a means of coping with inclement temperatures. During cool or cold days, a hypocaust or central heating system provided warmth within homes and other buildings such as public baths. Thick ceramic tile floors were supported by regularly placed pillars; the resultant underground chambers created by these pillars allowed the heat from a charcoal or wood fire to permeate the space and to radiate from the thick floor tiles into the spaces above. For Mediterranean and other moderate climates, this system performed well in providing heat for inhabitants of the Roman world.

The extensive building and construction projects of Rome led to urban planning. Their carefully planned cities consisted of a regular grid of streets intersecting at right angles. Main roads were flanked by sidewalks alongside domestic and commercial buildings, with open squares often covered with decorative mosaics. Commercial centers such as the forum, positioned near or at the city and placed near the intersection of two main streets, served as focal points, with an array of domestic, governmental, religious, and recreational buildings filling out the cityscape. These buildings usually shared some common architectural element or design so there was a uniformity to the various districts that reinforced the visual message that these were planned communities.

Impact

The effects of Roman architecture and building were both immediate and enduring. Without the urban-oriented technology that dominated much of Roman engineering, the culture known as ancient Rome would not have flourished. The many roads, bridges, stadia, public buildings, and water supply systems produced in the era aided in the operation and survival of the Roman world. Further, these engineering successes allowed the Roman Empire to expand and to dominate much of the known world in the years from 200 b.c. to a.d. 400

Roman engineers demonstrated the potential of simple technology matched to the astute management of workers, slave or free. Relying on a commitment from the society, these ancient engineers constructed projects that were built to last. For example, most major Roman roads were designed to be in service for a century, compared with the modern world's goal of 20-40 years. To this day, many amphitheaters, public baths, aqueducts, and bridges remain intact and in use throughout Europe and other areas that previously were part of the Roman Empire, from Britain to Asia Minor. The Roman installation at Bath, England, and the extensive ruins of Ephesus, Turkey, attest to the durability of Roman engineering. Because these skilled engineers were so successful in completing massive projects, the term "Roman project" has come to mean a viable large-scale engineering endeavor.

Because they were a pragmatic people, the Romans profited from diffusion and stimulus technology. Borrowing heavily from earlier civilizations, especially ancient Egypt and Greece, Roman engineers were able to perfect known techniques. In doing so, they replicated the style and refined the classical motif of colonnaded buildings, extended city planning, and introduced their own variation of the style with the use of the arch. Without a strong theoretical grounding to their work, these engineers sometimes produced "over-engineered" structures. These products of empiricism with their high margins of safety usually contained far more material than necessary for structural integrity and occasionally resulted in an overly heavy and cumbersome design. Although durable, these projects left a legacy that empiricism alone does not always produce the most elegant results.

The practical bent of Roman engineers manifested itself in another way as well. Aware that the products of their engineering ingenuity would require upkeep and continual attention, Roman designers provided means for maintenance technology in many of their structures. Projecting stones and cavities in walls as a permanent feature in things such as buildings and bridges made it easy to install scaffolding for the repair and maintenance of these items. Likewise, roads were monitored carefully for any problems that might cause structural weaknesses or deterioration so they could be repaired in a timely manner. This approach to maintenance technology carried over into the Medieval era, when cathedral builders incorporated features such as hidden stairways, exterior walkways, and passages to all sections of a building from the foundation to the spire to aid in the monitoring and maintenance of these stone churches.

Roman success with the technology of building and construction influenced the architectural style of several later eras. The basic basilica design, a rectangular building with carefully placed columns, was a prototype for many Renaissance churches and public buildings. The Romanesque style, incorporating semicircular arches and barrel vaults, also became a favorite for Mediterranean churches in the era. The success of the Romanesque design, along with the incorporation of the Roman dome, allowed the classical style to dominate much architecture in Renaissance Europe and in the emerging American republic. With their ordered columns, arches, vaults, and domes, many public buildings such as libraries, museums, city halls, state capitols, stadia, and monuments were copies of Roman designs. The graceful lines of a typical Roman semicircular arch bridge have made that style a favorite for many communities, including America's capital city of Washington, D.C., with its many bridges across the Potomac River. Indeed, the new American nation looked to classical Rome for many of its symbols and styles, from the eagle to the United States Supreme Court and the Capitol buildings. In addition, Thomas Jefferson, with his design of the library at the University of Virginia, took his inspirations from the Pantheon in Rome. The Roman classical style is so deeply ingrained into Western culture that for centuries many public buildings across the Western world were built with that architectural design.

Modern architects as well have embraced the arch and barrel vault as a motif for their buildings. H. Richardson, a renowned late-nineteenth-century architect, transformed American architecture with his neo-Romanesque style, which relied heavily on arches, stone exteriors, turrets, and vaulted spaces. Richardson's influence touched a wide range of projects, from warehouses to train stations, libraries, and churches throughout America. In the twentieth century, Louis Kahn incorporated the semicircle and vault in many of his designs, including the graceful Kimball Art Museum in Fort Worth, Texas, which is considered one of the most elegant buildings of its kind.

Beyond specific applications, the Roman record in technology left a legacy of the efficacy of empirical methods. Having both material and human resources, determination, ingenuity, and the ability to learn by using technology, the Romans achieved magnificent results. Relying on highly skilled craftsmen and artisans, the Romans, like many preindustrial societies, were able to produce massive, durable projects using relatively simple tools. Their ability to organize and manage large numbers of workers aided in their quest to provide a technology to serve both the urban and imperial Roman worlds.

Those talents were nurtured by a nation that used its architecture and engineering to expand the empire and to make a statement about the power of that empire. The impressive scale of many of Rome's monumental buildings were tangible reminders of the strength and ambitions of ancient Rome. In this way, engineering served the state in both functional and symbolic manners. The Pax Romana, that era in the which Rome dominated much of the Western world, was due in large measure to the ancient technology Romans borrowed and perfected. The extensive road and bridge systems, arenas and stadia, public baths and other civic buildings, aqueducts, fortifications, and monuments served to unify the disparate elements of Rome's world. In the process, Romans spread and adopted various technological methods so that even the far reaches of the empire mirrored the life style and physical artifacts of the society, much as the influence of the American dominance in the last half of the twentieth century spread throughout the globe.

The legacy of Roman architecture and engineering is enduring. Beginning with the heritage of earlier Greek classical designs and methods, Roman engineers gradually modified, refined, and improved on these inherited styles. Especially in their use of the arch and of concrete, the Romans created their own unique architecture, which played a key role in serving the needs of an urban culture and an empire. The vastness of their projects, from aqueducts to arenas, and the ingenuity of their methods earn them an impressive reputation as very successful engineers. The durability of that technology and the degree to which it spread through the Roman Empire attest to its usefulness and functional design. Because they used empirical methods, Roman engineers demonstrated the value of that kind of technology; anyone who experiences an original Roman structure is deeply impressed with the craftsmanship, artistry, and architectural insight that made it possible. The hallmarks of Roman architecture and engineering impressed people of the classical era and of many later periods, including Renaissance Europe and the new nation of America. The achievements of Rome remind us that through determination, dedication, skill, simple technology, and the prudent management of large labor forces, this society created magnificent results. They also provided the basis for future urban planning, for urban-based technology, for the creation of large-scale projects, and for a distinctive and widely copied architectural style. Those achievements continue to generate awe and admiration and stand as one of the most significant engineering triumphs of the preindustrial world.

H. J. EISENMAN