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The Colosseum and the Invention of Concrete

The arch became the essential element in Roman architecture, emphasizing the strength and massiveness of the masonry structure as if to symbolize the sustaining power of the empire itself - most obviously in the triumphal arches erected in honour of emperors (see pp. 214-16). Arches enframed by engaged columns and entablatures -used from early in the first century BC - were a dominant motif in the imperial period. The exterior of the great Flavian amphitheatre, known since the eighth century as the Colosseum, is entirely composed of them in arcades which integrate the units of the design by rhythmic horizontal and vertical repetition (5,43; 44). The orders follow the ascending sequence established by the Romans for multi-story buildings - Doric-Ionic-Corinthian. (The sequence is purely aesthetic, the Doric being visually the heaviest and strongest and the Corinthian the lightest.) Although several such permanent arenas for gladiatorial combats and other spectacles had been built elsewhere, somewhat surprisingly this was the first in the city of Rome, where 'games' had previously been held in the forum or in temporary structures. With a seating capacity estimated between 45,000 and 55,000, the rapid

entrance-exit problem for filling and emptying the vast seating space was formidable. It was brilliantly solved by an ingenious arrangement of stairways and corridors all leading down to the continuous ground-floor arched openings (5,45). The Colosseum was begun as a shrewd bid for popularity by Vespasian, the first emperor of the Flavian family, who came to power in AD 69 as the result of a mass uprising against Nero, the last of the dynasty established by Augustus. To fulfil its purpose it had to be built quickly: the enormous structure, which is on an elliptical plan measuring 615 by 510 feet (188 by 155m) externally and 159 feet (48m) high, was completed in no more than a decade. Various materials were used: concrete for the 25-foot-deep (7.5m) foundations, travertine (a fine local limestone lighter in weight and less strong than marble, easily cut when first quarried, but hardening with exposure to air) for the framework of load-bearing piers, tufa and brick-faced concrete for radial walls between the piers, travertine for the exposed dry-jointed stonework held together by metal clamps (most of which have gone) and marble (of which no trace remains today) for the interior. A giant awning to protect spectators from the sun was supported on wooden poles projecting inwards from the top and manipulated by ropes tied to bollards on the pavement surrounding the building.

The Colosseum is an outstanding work of Roman engineering as well as of architecture. In both design and structure it was, however, conservative. Concrete was used simply for foundations and walls, as it had been in many earlier buildings, including, for example, the sanctuary at Praeneste. Roman concrete (opus caementicum) was a combination of mortar and pieces of aggregate (caementa) laid in courses - unlike modern concrete, which can be mixed and poured. Its unique strength and durability derived from the binding agent, a mortar made of lime and volcanic sand, first found at Pozzuoli near Naples and thus called pozzolano, used as early as the third century BC. Exposed walls of this concrete were usually faced with another material, an irregular patchwork or neatly squared pattern of stone and later, under the empire, brickwork. The full potentialities of the material were, however, only gradually discovered. In early examples the cement dried out quickly so that each layer formed a single horizontal band like an enormous stone slab. But the development, about the time of Augustus, of a slow-drying mortar, probably made with volcanic sand found near Rome, produced a concrete core that hardened into an inert homo-geneous mass. This revolutionized architecture for, when combined with the arch and vault, it enabled the Romans to cover, without any interior support, spaces far larger and of far greater flexibility of form than had ever been possible before. Ancient Egyptian, Mesopotamian and Greek architecture had been essentially an art of composition in mass. Space was simply what was left over or left between the solids. This negative conception was now replaced by that of an architecture of space. A building was conceived as a shell molding space into whatever shape the architect or his patron desired.



 

The earliest building in which the possibilities of using concrete for this new 'spatial' conception of architecture are known to have been explored is the Golden House designed for the Emperor Nero (AD 54-68) by an architect named Severus. Of the parts that remain, the most interesting is a group of rooms which, although divested of all their surface decorations apart from some traces of delicate stucco-work, reveal a truly revolutionary originality (5,46). An octagonal space covered by a rather shallow dome is surrounded on five sides by rectangular vaulted rooms, one of which terminated in an ornamental cascade of water. Lighting, unusually bright and even for a Roman interior, was provided by a circular opening or oculus in the centre of the dome and, very ingeniously, by clerestory windows high up on the walls of the radial rooms. The inner surface of the dome was probably decorated with mosaics, which must have given an almost magically insubstantial effect. And the views through the wide square openings of the octagon from one room to another and on to the garden to the south may well have seemed to realize architectural prospects of the type that Pompeiian painters had feigned. For here the walls really had been broken and bent to permit free spatial flow and to give the appearance of an unending series of opulent chambers. From no single point would it have been possible to grasp and resolve the visual complexities and ambiguities of this highly sophisticated interior.

The surviving ruins are no more than a small part of the Golden House, in which, Nero remarked, he could 'at last begin to live like a human being'. His biographer Suetonius (AD 69-140) described the main banqueting hall, which 'constantly revolved, day and night, like the heavens'. The remark is tantalizingly brief, but it is usually assumed that the ceiling - not the room itself - revolved and was constructed in the form of a vast wooden dome decorated with stars or astral symbols, a kind of planetarium beneath which the emperor entertained his guests at the very centre of the cosmos, as it were. The idea of placing such a cosmic canopy over a ruler with pretensions to universal authority probably derived from the royal tents and canopies of Achaemenid Persia. It would certainly have appealed to Nero; and it may well lie behind the domes that became such a prominent feature of imperial Roman architecture. The development of the concrete dome may even have entrance-exit problem for filling and emptying the vast seating space was formidable. It was brilliantly solved by an ingenious arrangement of stairways and corridors all leading down to the continuous ground-floor arched openings (5,45). The Colosseum was begun as a shrewd bid for popularity by Vespasian, the first emperor of the Flavian family, who came to power in AD 69 as the result of a mass uprising against Nero, the last of the dynasty established by Augustus. To fulfil its purpose it had to be built quickly: the enormous structure, which is on an elliptical plan measuring 615 by 510 feet (188 by 155m) externally and 159 feet (48m) high, was completed in no more than a decade. Various materials were used: concrete for the 25-foot-deep (7.5m) foundations, travertine (a fine local limestone lighter in weight and less strong than marble, easily cut when first quarried, but hardening with exposure to air) for the framework of load-bearing piers, tufa and brick-faced concrete for radial walls between the piers, travertine for the exposed dry-jointed stonework held together by metal clamps (most of which have gone) and marble (of which no trace remains today) for the interior. A giant awning to protect spectators from the sun was supported on wooden poles projecting inwards from the top and manipulated by ropes tied to bollards on the pavement surrounding the building.

The Colosseum is an outstanding work of Roman engineering as well as of architecture. In both design and structure it was, however, conservative. Concrete was used simply for foundations and walls, as it had been in many earlier buildings, including, for example, the sanctuary at Praeneste. Roman concrete (opus caementicum) was a combination of mortar and pieces of aggregate (caementa) laid in courses - unlike modern concrete, which can be mixed and poured. Its unique strength and durability derived from the binding agent, a mortar made of lime and volcanic sand, first found at Pozzuoli near Naples and thus called pozzolano, used as early as the third century BC. Exposed walls of this concrete were usually faced with another material, an irregular patchwork or neatly squared pattern of stone and later, under the empire, brickwork. The full potentialities of the material were, however, only gradually discovered. In early examples the cement dried out quickly so that each layer formed a single horizontal band like an enormous stone slab. But the development, about the time of Augustus, of a slow-drying mortar, probably made with volcanic sand found near Rome, produced a concrete core that hardened into an inert homo-geneous mass. This revolutionized architecture for, when combined with the arch and vault, it enabled the Romans to cover, without any interior support, spaces far larger and of far greater flexibility of form than had ever been possible before. Ancient Egyptian, Mesopotamian and Greek architecture had been essentially an art of composition in mass. Space was simply what was left over or left between the solids. This negative conception was now replaced by that of an architecture of space. A building was conceived as a shell molding space into whatever shape the architect or his patron desired.



 

The earliest building in which the possibilities of using concrete for this new 'spatial' conception of architecture are known to have been explored is the Golden House designed for the Emperor Nero (AD 54-68) by an architect named Severus. Of the parts that remain, the most interesting is a group of rooms which, although divested of all their surface decorations apart from some traces of delicate stucco-work, reveal a truly revolutionary originality (5,46). An octagonal space covered by a rather shallow dome is surrounded on five sides by rectangular vaulted rooms, one of which terminated in an ornamental cascade of water. Lighting, unusually bright and even for a Roman interior, was provided by a circular opening or oculus in the centre of the dome and, very ingeniously, by clerestory windows high up on the walls of the radial rooms. The inner surface of the dome was probably decorated with mosaics, which must have given an almost magically insubstantial effect. And the views through the wide square openings of the octagon from one room to another and on to the garden to the south may well have seemed to realize architectural prospects of the type that Pompeiian painters had feigned. For here the walls really had been broken and bent to permit free spatial flow and to give the appearance of an unending series of opulent chambers. From no single point would it have been possible to grasp and resolve the visual complexities and ambiguities of this highly sophisticated interior.

The surviving ruins are no more than a small part of the Golden House, in which, Nero remarked, he could 'at last begin to live like a human being'. His biographer Suetonius (AD 69-140) described the main banqueting hall, which 'constantly revolved, day and night, like the heavens'. The remark is tantalizingly brief, but it is usually assumed that the ceiling - not the room itself - revolved and was constructed in the form of a vast wooden dome decorated with stars or astral symbols, a kind of planetarium beneath which the emperor entertained his guests at the very centre of the cosmos, as it were. The idea of placing such a cosmic canopy over a ruler with pretensions to universal authority probably derived from the royal tents and canopies of Achaemenid Persia. It would certainly have appealed to Nero; and it may well lie behind the domes that became such a prominent feature of imperial Roman architecture. The development of the concrete dome may even have been stimulated by the symbolism of the textile or wooden cosmic canopies of the East.

The Emperor Domitian (AD 81-96), whose palace on the Palatine Hill in Rome exhibits similar flexibility of planning, used the new technology to provide an appropriate setting for his imperial rule. Trajan (AD 98-117), who ruled for the 20 years during which the Roman empire reached the peak of its power and its greatest extent, was more concerned with public works. The most notable were public baths, of which unfortunately little survives, and a new commercial quarter known as Trajan's Market, created by cutting away the slope of the Quirinal Hill. Trajan's Market is one of the most fascinating of all surviving Roman structures, at once logical and complex, utilitarian but possessing an austere monumental beauty. One hundred and fifty or more shops and offices on three different levels connected by streets and steps are combined with a great covered market hall (5,47). Built for a city most of whose inhabitants were engaged exclusively in working for, buying from and selling to one another, it had a social importance hard to exaggerate. The concave main facade was articulated with pilasters, but the rest of the exterior and the interiors were severely simple, of brick-faced concrete with travertine surrounds to rectangular doors and windows. A better idea can be obtained from them than from the numerous but much less well preserved remains at Ostia and elsewhere of the architectural form and appearance of Roman multi-story construction. At street level there are shops with small windows above giving light and air to timber-floored mezzanines or garrets approached from within the shops by timber ladders. The main horizontal divisions, however, are concrete barrel vaults between the party walls, and access to the upper stories is by concrete stairways. (Concrete was made compulsory for floors and stairways after the great fire of AD 64.) Great ingenuity was applied to the planning. The architect's aim was eminently practical: to provide the maximum space, well lit and aired, for the various activities connected with buying and selling within a limited area on an extremely awkward sloping site. The result is a rare achievement of volumetric organization, an autonomous structure of interlocking curved corridors, straight streets and passages, and vaulted rooms of different sizes (5,48). Nowhere else - except in the Pantheon - can the characteristically Roman genius for molding space be better experienced.

 

The Pantheon

The Pantheon was built under Trajan's successor, the Emperor Hadrian (AD 117-38), on the site of an earlier temple, which had been of an entirely different design but similarly dedicated to all the gods by Marcus Agrippa (see p. 202), whose name is boldly recorded on the facade (5,49; 5°)- It consists of two parts, a traditional rectangular temple-front portico with massive granite columns, and an enormous domed rotunda of a size made possible by the development of slow-drying concrete. The awkwardness of the join between these two parts would have been much less evident originally, when the building was not freestanding as it is today, but was approached on axis through a colonnaded forecourt, which screened all but the portico. The ground level was much lower also, so that five wide marble steps had to be mounted to reach floor level. Yet the contrast - or unresolved conflict - between the rectangularity of the portico and the circularity of the rotunda, between the exterior architecture of mass and the interior architecture of space, must have been even sharper because largely concealed, and the visual excitement and feeling of sudden elation experienced on passing through the door must have been even more overwhelming. One passes from a world of hard confining angular forms into one of spherical infinity, which seems almost to have been created by the column of light pouring through the circular eye or oculus of the dome and slowly, yet perceptibly, moving round the building with the diurnal motion of the earth (5,51).

This exhilarating space is composed, as Vitruvius had recommended for a rotunda, of a drum the height of its own radius and a hemispherical dome above - diagram-matically a sphere half enclosed in a cylinder, the total height of 144 feet (44m) equal to the dome's diameter. The effect is not, however, that of geometrical solids. The lower part of the drum wall is pierced by niches which suggest continuity of space beyond; the columns screening them have lost even the appearance of being structural supports: they seem more like ropes tying down the dome, which floats above. The surface of the dome is broken by five rings of coffers very ingeniously molded to give the illusion that they are rectangular and that, although they diminish in area, all are of equal depth. To achieve this effect, account had to be taken of the dome's curvature - which presented a tricky geometrical problem, for no straight line can be drawn on it - as well as of the shadows cast by light from above and of the sbectator's ansle of vision from the ground. Originally, these coffers probably had gilded moldings around their edges and enclosed gilt bronze rosettes.

Minor changes were made to the interior in about 609, when, as the reigning Pope Boniface IV put it, 'the pagan filth was removed' and the temple converted into a Christian church - to which, of course, its extraordinary and unique preservation is due. In the 1740s the attic zone (i.e. the band of wall immediately beneath the dome), which had fallen into disrepair, was insensitively stuccoed and provided with overlarge false windows. Otherwise the interior is substantially intact. The various types of marble, mainly imported from the eastern Mediterranean and used for the pattern of squares and circles on the pavement, for the columns and the sheathing of the walls - white veined with blue and purple (pavonazzo), yellowish-orange (giallo antico), porphyry (see Glossary) and so on - still reflect and color the light that fills the whole building.

That the Pantheon should eventually have been made into a place of worship for monotheistic Christians was not wholly inappropriate. It was built at a moment of religious speculation and exploration, when faith in traditional beliefs was giving way increasingly to Eastern mystery cults, and its design marks a break with the traditional form of Roman temple, which, as we have seen, harked back to Etruscan and Greek prototypes (p. 199-202). Less than a century after its completion the historian Dio Cassius (c. 155-c. 235) pondered its significance, remarking that it was called the Pantheon 'perhaps because it received among the images which decorate it the statues of many deities, including Mars and Venus; but my opinion of the name is that, because of its vaulted roof, it resembles the heavens'. He appreciated that the images of individual gods were of less importance than the building itself, within which the supreme god, so often associated with the sun, was immanent, visible yet intangible in the light streaming through the oculus and moving over the surface of the dome. It was, in fact, not so much the temple of a specific religious cult as an attempt to express the very idea of religion, of the relationship between the seen and the unseen, between mortals and the inscrutable powers beyond their ken. Domes had previously been decorated to symbolize the heavens, but no single building embodied this idea more effectively and on a grander scale than the Pantheon. Nor did any exert greater influence on subsequent developments in the religious architecture of the West. Domes and half-domes as symbols of heaven had become essential features of Christian churches long before the Pantheon itself was converted into one.

ROMAN SCULPTURE

The Pantheon is quintessentially Roman. But the Emperor Hadrian, to whom its design has sometimes been attributed, displayed more eclectic tastes in his enormous, rambling imperial residence outside Rome - Hadrian's Villa near Tivoli. A philhellene who spoke Greek better than Latin and preferred Athens to Rome, Hadrian furnished the villa throughout with Greek statues. Several hundred, perhaps as many as 1,000, survive in fragments now scattered among the museums of the world. They are mainly copies or variants of Classical Greek or Hellenistic figures or groups. The only original works seem to have been portraits of Hadrian himself and his favourite Antinous, a youth from Asia Minor who was mysteriously drowned in the Nile in AD 130 and promptly numbered among the gods. Images of Antinous, set up all over the empire, were, however, more often than not pastiches in which earlier statues of Hermes, Dionysus or other gods were combined with heads portraying the youth's sultry and often rather sulky good looks (5,52).

In his obsession with Greek sculpture Hadrian followed a long and well-established tradition. Romans had begun to collect Greek statues before the end of the third century BC, and after Greece was absorbed into the Roman empire as the province of Achaia in 146 BC the flow of Greek sculptures westwards was continuous. The sanctuary at Delphi alone is said to have been robbed of some 500 statues. Even so, the demand in Rome far exceeded the supply. In letter after letter Cicero, for example, implored a friend who was living in Athens to procure sculpture for him. He was building a country house near present-day Frascati, a few miles outside Rome, and needed some sculpture to adorn it. A great deal of sculpture was bought in this way as 'furniture pieces' and was doubtless produced specifically for this market - hence the proliferation of copies and imitations and their usually rather poor quality. (It is on these shaky foundations, it should be remembered, that much of our knowledge of Classical Greek sculpture rests.) They were mostly produced in Greece - either in Athens itself, the Greek islands or the Greek cities on the coast of Asia Minor - or by immigrant Greek artists in Rome. Sometimes these sculptors seem to have worked from casts with the aid of pointing apparatus (see Glossary). But they had no respect for either medium or scale. Bronzes were reproduced in marble, with the addition of unsightly supports as a result, and scale was adjusted arbitrarily to suit the decorative demands of the purchasers. Statues were even copied in reverse to make up pairs. A mid-fourth-century BC statue by Skopas, which, Pliny tells us, was 'worshipped with extremely sacred ceremonies at Samothrace', was duplicated in this way to fill balancing niches in a Roman house of the imperial period. There could hardly be a more telling instance of the transformation of a Greek devotional image into a luxury ornament.

It is seldom known how faithfully a marble of the imperial period reproduces an earlier original (the caryatids from Hadrian's Villa and from the Forum of Augustus are the only Roman copies that can be compared with the still surviving originals), and there is reason to believe that some were essays in earlier styles rather than copies - including two of the most famous of all, the Apollo Belvedere (5,5) and the Laocoon (5,53). The latter derives stylistically from the relief of similarly straining muscular figures with tortured faces on the frieze of the Altar of Zeus from Pergamum (5,17) and was for long regarded as a copy after a lost work of that period. That it is an original work of the first century AD is strongly suggested by the recent discovery (at Sperlonga, south of Rome) of very similar groups signed by the three sculptors to whom Pliny attributed the Laocoon, and almost certainly carved expressly for a grotto used as a banqueting hall by the Emperor Tiberius (AD 14-37). The incident represented by the Laocoon is not recorded in Greek literature in just this form; the earliest known source for it is the greatest of all Latin poems, Virgil's patriotically Roman Aeneid (written c. 27-20 BC), where Laocoon appears as the Trojan priest who warned his fellow countrymen against admitting the wooden horse of the Greeks into their city. While he was sacrificing a bull to Poseidon, Virgil relates, two serpents swam out of the sea, coiled round him and his sons and killed them. As the Romans believed themselves to be descended from the Trojans, the heroic suffering of Laocoon had special significance for them. The priest and his sons are at once figures from the mythical prehistory of Rome and symbols of human fortitude in a struggle against malign, incomprehensible supernatural forces. In turning to Hellenistic art for inspiration, however, the three sculptors, who came from Rhodes, introduced a declamatory sensationalism, both technical and emotional, which ill accords with the dignity, restraint and gravity of the Aeneid.

If Roman cultural dependence on Greece was evident even in a major original work like the Laocoon, which stood in the imperial palace when Pliny saw it, it became quite blatant in the practice of making full-length portrait statues by the simple expedient of adding a portrait head to a body copied direct from a Greek original. The bodies were produced independently and could be bought, as it were, from stock. A variety of poses and types and sizes were available to choose from, each with a socket in the neck so that a portrait head could be attached. How prevalent the practice was - and how indifferent the Romans were to its demeaning implications - is shown by its use for prominent imperial portraits, though sometimes, it is true, with such latitude that the resulting image has the force of an original conception. The statue of Augustus, which originally stood outside the imperial villa at Primaporta near Rome, is the best known of these (3,54). For it the famous Doryphorus (4,34), an accepted exemplar of ideal male proportions, was treated more freely than usual, almost, in fact, as if it were a tailor's dummy. Not only the portrait head but a Roman general's costume was added as well, including the cuirass crisply carved with allegorical figures probably alluding to the diplomatic victory over the Parthians in 20 BC. Adjustments were also made to the pose, notably by raising the right arm to a speaking gesture. By these means a highly idealized statue of an anonymous nude athlete was transformed into an image of imperial power personified by Augustus, a Greek model into what seems to be a characteristically Roman work of propagandist art - though it may well have been carved by a sculptor of Greek origin.


Date: 2015-12-24; view: 732


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