Roman architecture was distinctive because it brought highlydeveloped engineering skills to bear on large-scale buildings. TheRomans made huge strides in engineering, building great aqueducts,large temples, amphitheaters and other structures, some of which arestill standing. They did this with the help of materials such as concreteand with innovative structures such as vaults and domes.
The Romans borrowed heavily from the Greeks in many aspects of their culture, andtheir architecture was no exception. They built temples that looked like Greek temples,surrounding them with rows of columns built according to the orders. But the Romansmade advances in engineering and building technology, and it is in these areas that theydeveloped some of the most long-lived architectural ideas.
Probably their most influential idea was concrete, which is easy tothink of as a modern invention even though it has been around since Roman times. In factit was not strictly a Roman idea—both the ancient Greeks and the people of Campania(the part of southern Italy where Greeks and Etruscans had settled) were using mortar intheir stone walls at least as far back as the fourth century BC. But the Romans were goodat picking up an idea and running with it, and that is what they did with concrete.
Creating the precise curves needed to build a vault is a difficult business,especially if you only have stones and ordinary mortar to build with. You have toput up supporting timber formwork, known as centering, cut each stone verycarefully and precisely and then lay the stones carefully on top of the timber. Onlylong afterward, when the mortar has set hard, can the centering be removed. Withconcrete, however, the centering could be much lighter in weight and there wasless skill involved in building the vault above it. Since the concrete set quickly, thecentering could be removed sooner and the job finished faster.
It was the perfect material for a fast-growing empire, where buildings needed to be putup at speed. When they wanted to build a thick, solid wall quickly, Roman builders useda mixture of rubble mixed with concrete, facing it with brick or dressed stones—theresult was cheap, fast to build and very strong. Concrete was also ideal for building thecurved shapes—especially those of vaults and domes—that the Romans liked so much.
And the Romans developed a way of making a very special kind of fast-setting, water-resistant concrete that was ideal for building bridge piers.
Concrete has been described as a mortar that is mixed with small stones tocreate a solid, hard mass. It is normally made up of three elements: the aggregate (sandplus stones), the cement (a binding material) and water. The magic was in the bindingmaterial, and the Romans discovered an especially effective one—a mixture of lime anda type of volcanic ash known as pozzolana.
One of the greatest of all Roman buildings is the Pantheon (below), a temple to all the gods, built in the center of Rome itself. The Pantheon is a circular building roofed with a dome and the interior of the dome, with its pattern of recessed squares (an effect called coffering) is stunningly beautiful. None of this could have been achieved without the careful use of concrete, the main material of the dome. In particular, the builders varied the aggregate used in the concrete, using heavy travertine and tufa for the foundation and the walls up to the first cornice; lighter brick and tufa for the next level; then brick alone; and finally in the topmost part of the dome an even lighter material, volcanic pumice.
Pozzolana came from the hills around the Bay of Naples, the area known as Puteoli or Pozzuoli. The Romans regarded pozzolana with awe and there are descriptions of its properties in the writings of both Pliny (Natural History 35.166) and Vitruvius, who, in his treatise on architecture, points out its key qualities: “This material, when mixed with lime and rubble, not only furnishes strength to other buildings, but also, when piers are built in the sea, they set under water.” And Vitruvius was right. Roman concrete is so strong that, a thousand years after they were built, and after the masonry facing has been robbed or weathered away, the concrete cores of many Roman buildings still survive.
“… they were naturally devoted to building and that was the favorite extravagance of the rich.” J.C. Stobart, The Grandeur That Was Rome
So concrete made with pozzolana was ideal for bridge building. This was important because stone bridges were very difficult to build without fast-setting concrete. In fact, most bridges before the Romans were either very small-scale stone- clapper bridges across streams or wooden structures that had a limited life. So Roman concrete transformed bridge building.
Arches and domes
But its usefulness went further than this, taking Roman architecture in directions unthought of by the Greeks. In particular, it was ideal for creating structures that were curved. Domed buildings, such as the great temple of the Pantheon in Rome or the vast imperial bath-houses, vaulted buildings such as the Romans' great basilicas and all types of arched structures, were made much more feasible with the use of concrete.
None of these structures was a Roman invention—the Greeks had built domes and vaults before the rise of Rome. But what was significant was the way the Romans extended and developed their use, creating vast domes, such as the one roofing the Pantheon, and huge arched structures. It was the Romans, devoted to building and determined to make ever larger and more magnificent monuments, who made these types of structures into great architectural ideas and developed their huge potential. They transformed the architectural scene.