The Colosseum (17 page)

23. A contemporary cartoonist captures the ‘battle of the Colosseum’ in the early nineteenth century. Fea stands in the water, holding up the literary texts which supported the idea that the building had been flooded for naval battles. His adversaries wield plans and inscriptions against him from dry land.

In many of these old archaeological arguments one suspects that, if one had been a participant oneself, one would have been on what is now seen to be the wrong side. It frankly would have seemed far more sensible to dismiss this warren of walls as a medieval insert and to imagine all the activity in the Colosseum – land- or water-based – taking place on the firm ground underneath it (after all, because of the flooding which put a stop to the excavations, Fea did not know exactly how deep the substructures went). An arena floor perched on a web of rough masonry would have seemed a very odd idea indeed. We have a strong feeling that in 1814 we would have been with Fea (just as we would probably have been with the Cambridge Professor of Greek Richard Jebb, who at the end of the nineteenth century dismissed some of the prehistoric remains excavated by Heinrich
Schliemann at Mycenae as a Byzantine slum). But whatever the strength of the arguments on all the different sides, this Colosseum controversy is distinctive for highlighting the problems of interpreting the building that have not significantly changed over 200 years. The issue still is how do you stitch together the different forms of evidence – literary, archaeological, as well as ‘common sense’ views of how the building must have been used – which do not actually quite fit. Can you massage away the contradictions? With all our more extensive knowledge of the structure of the Colosseum and more sophisticated archaeological dating techniques, the modern orthodoxy is still a version of the Pacifier’s compromise: that the substructures are ancient, but were not in place at the very beginning of the building’s history. The arena floor was elevated at its current height, but more simply – so allowing Dio’s claim about naval battles to be right.

But
was
Dio right? For all the up-to-date careful analysis and new discoveries (including what appear to be patches of waterproofing on the surfaces of the cavity below the level of the arena), we still do not know. It partly depends on how grandly to interpret the spectacular Dio refers to: large boats manoeuvring on a substantial depth of water, or a rather more Toy Town affair in an overgrown paddling pool? But more than that, it depends on a good answer to the question of water supply. Even with the paddling-pool model, we are not sure how the space of the arena could have been filled with water, and drained again, at reasonable speed. One suggestion, which involves using sluice-gates and backflow water from the Tiber, would also have had the effect of bringing quantities of sewage into the arena along with the water. Hardly the image of lavish and luxurious spectacle that
Martial’s poetry would have us believe. Certainly a naval battle with a difference.

PLANS AND SPECIFICATIONS

For the design of the Colosseum, water was mainly a problem in a quite different sense. It may be hard to see now how any spectacular sequences of flooding and draining were arranged for the shows. But on a day-to-day basis the pressing issue was how to prevent the Colosseum as a whole, constructed as it was in a river valley, reverting to the lake that the site had been under the emperor Nero. Besides, the building itself acts as a huge water barrel: rainfall on the seating and arena, sometimes torrential, has to be drained away, otherwise up to 175 litres of water a second would accumulate during a heavy storm. One of the most extraordinary – albeit unseen – achievements of the Colosseum’s designers is to have arranged the drainage. Recent archaeological work on the water system has revealed an intricate network of underground drains, around and through the centre of the monument. The ring drain in fact runs 8 metres below the valley floor and takes the water off to flow into the Tiber. Before they even thought about the foundations, the designers had expertly arranged the site’s hydraulics. Obvious as it is, this raises the question of the architectural and constructional skills necessary for such a huge enterprise. Or to put it as most visitors would when they confront this vast structure: how on earth did the Romans build it?

The usual answer is to stress the combination of vast quantities of slave labour (skilled and unskilled), long traditions of practical craftsmanship and a high level of technical
and theoretical architectural expertise on the part of the principal designers. That is broadly correct. We can deduce from a minute examination of the Colosseum’s structure and dimensions how an over-arching plan of considerable sophistication (though, at the same time, drawing heavily on traditional designs) was executed by teams of more or less expert workmen.

Part of the trick was to use, and adapt, relatively simple ratios and standard units. It seems that the ideal ratio of length to width for the arena itself was 5:3. According to one plausible recent reconstruction, the original plan for the Colosseum was to have an arena 300 Roman feet long by 180 Roman feet wide. The convention, as we can observe in other amphitheatres, was to make the width of the auditorium equal to the width of the arena, which would have given a total length of 660 Roman feet (300 + 360), a total width of 540 Roman feet (180 + 360) and a circumference to the whole building of 1885 Roman feet – as an architect could have calculated through relatively simple trigonometry. Did this matter? Yes, because the size of the perimeter intimately affects the design and number of the external arches. A grand amphitheatre had to have a number of grand entrances and the convention, it seems, was for the arches of those entrances to be 20 Roman feet wide (a convention that would have made it easier to instruct the artisans). The Colosseum was to have eighty arches, which – if the 20-Roman-foot standard was to be preserved and allowing for the width of the columns themselves – meant reducing the perimeter slightly, to 1835 Roman feet. This was achieved by leaving the size of the auditorium, and so of the audience capacity, intact, but reducing the size of the arena to 2802 × 168 Roman feet
(still in the ratio 5:3). In other words, the architects balanced the need for size and scale against the desire to work to simple and familiar ratios and intervals.

This meant that on the ground they could leave teams of artisans and their foremen with a clear plan, which would not need much hands-on supervision from the overall designer. We can see by examining the individual arches on the exterior how much the details of execution could vary from example to example. The vertical jointing patterns are quite different from pier to pier, presumably reflecting variety in the size of travertine blocks delivered from the quarries or sawn on site, and measurements that were not crucial to the overall structure could differ from arch to arch by as much as several centimetres. Likewise it seems that in the design and building of the stairways, the individual teams and perhaps under-architects had a good deal of independence. On the other hand, the voussoirs in the arches – crucial to the stability of the structure – are close to identical, and the outermost annular corridor on the ground floor is 5 metres wide and varies along its entire length by less than 1 per cent. Where it mattered, Roman architects or their design team could ensure absolute precision from their workforce.

So far, so good. But this reconstruction of the principles of working methods tends to conceal how little we know about the identity of those who designed the building: the myth about the architect being a Christian by the name of Gaudentius is just that, a myth; we have no clue who was in charge of the project. It also conceals how little we know about the methods and skills involved in the design. Despite the survival of a first-century architectural handbook by Vitruvius, our understanding of how Roman architects actually
went about their work, and what the balance was between traditional practical craftsmanship and highly technical calculations of loading, proportion, lines of sight and so forth, is largely based on guesswork. We have a few traces of ground plans (preserved on inscriptions) and a handful of three-dimensional models of buildings which may have been made by architects to guide the builders on site or to inform (and please) the client. But it is very little to go on. We also read the odd anecdote about architects and their imperial clients, which make various allusions to drawings and plans, as well as to the perilousness of a design career under the emperors. It is said, for example, that Apollodorus, the emperor Trajan’s favourite architect, when explaining some architectural details to his client, was interrupted by the young Hadrian. Unimpressed with the young man’s architectural expertise, he told him brusquely to ‘get back to his stilllifes’. Later, when he had become emperor himself, Hadrian sent to Apollodorus his own plans for a new temple, ‘to show that a great work could come about without his help’. Apollodorus was predictably dismissive of the emperor’s schemes and paid for his candour with his life. What the relationship was between Vespasian and Titus and their anonymous architect – whether or not we should envisage top-level meetings with the clients keenly discussing plans, sketches and models – we can only guess.

There is a sense also in which talk of ratios, units of measurement, traditional craftsmanship and slave labour makes the whole process of construction seem rather too easy. To appreciate the extraordinary scale of the labour, it is worth looking once again at the work and planning involved in those parts of the scheme that were never intended to be
visible. For after the complex drainage network, before the building could ever get off the ground, came the foundations.

The Colosseum’s deepest foundations are roughly in the shape of a doughnut. Under the walls and seating they are a full 12 to 13 metres deep, and – for safety’s sake – this depth of underpinning continues for 6 metres outside the perimeter wall, under the pavement. Beneath the arena itself, however, the foundations are shallower, only about 4 metres deep. Simply digging the hole, an oval, about 200 metres × 168 metres and probably 6 metres deep, with pick and shovel was a huge enterprise. It seems likely that some of the excavated earth was used to raise the ground level around the whole building by about 6.5 metres, so that the new amphitheatre stood up proud in its valley setting. (The whole valley floor had already been raised 4 metres with debris from the great fire of Rome in
AD
64.) The rest of the spoil from the huge hole, 100,000 cubic metres, that is about 220,000 tonnes of it, had to be carted away in ox-carts, lugging 500 kilos at a time at a speed of less than three kilometres an hour, to the port along the river Tiber. No mechanical diggers, no 30 tonne trucks; only sweat and muscle.

Once the whole area had been excavated, another huge labour began. Two great perimeter walls (one 539 metres, the other 199 metres long), 3 metres thick with a rubble core, 12.5 metres high, retained the solid concrete and rubble foundations. Once the retaining walls had been built, the remaining hole – over 250,000 cubic metres in volume – was filled with concrete, lime, mortar and sand mixed with water and volcanic rock. It is only in the last few years that archaeologists have managed to take core samples from these underpinnings and to establish their make-up and dimension. Much
work remains to be done, but the main point is already clear: the Colosseum still stands because it was built on very solid foundations indeed.

Even with all this detail, the scale of the work on just this preliminary phase of construction may still be hard to grasp. In order to bring it rather closer to home we asked a firm of Chartered Quantity Surveyors in 2004 to estimate the costs of creating the Colosseum’s foundations in England then, using modern methods and materials. The specification was as follows:

The site is flat, filled with compacted clay, with good but citycentre road access.

Dig a hole 6 metres deep, in the shape of an oval (A) 198m
×
178m.

An inner oval (B) on the same axes, 80m
×
47m, needs to be only 4m deep.

Around the outer perimeter (A) construct a brick-faced wall with cement and rubble fill 539m long, 3m wide and 12.5m high.

Around the inner perimeter (B) construct another brickfaced wall with cement and rubble fill, 199m long, 3m wide and 12.5m high.

Fill the oval (A) between outer and inner perimeter walls with cement plus stone or broken brick to a height of 12.5m, volume 262,467m
³
.

Fill the inner oval (B) with cement and broken brick or stone to a depth of 4m, volume 11,772m
³
.

Use part of the excavated spoil (152,003m
³
) to raise the ground level for 40 metres outside the external perimeter wall (A) from 16m above sea level (asl) to 22.5m asl. This will use about 50,000 m
³
of the spoil.