The Structure of the Colosseum

The structure of the Colosseum is incredible, particularly given its age. It leveraged the accumulated knowledge of Roman construction and building materials. Knowing how Emperor Vespasian was very careful with his money and with rebuilding the Empire, so it is clear that the primary purpose of the Colosseum was socio-political: As the hated Nero hadn’t left a good impression on the population Vespasian was keen to show that emperors could also give as well as take. The structure of the Colosseum and the activities within it were an opportunity to pull Roman society together.

A plan view showing the structure of the Colosseum

The Colosseum is elliptical in plan with its axes about 620x513ft in length (about 190x156metres). It is about 165ft in height (50m, in fact, I think it is almost exactly 48.5m). The internal arena was 287x180ft (about 88x55m). Estimates on the number of spectators vary but generally speaking it could seat 45 to 50,000 spectators and on special occasions, the numbers could be as high as 70,000.

In order to construct the Colosseum, a skeleton framework of concentric piers and arches was built of Travertine limestone. These rings were linked with walls. Different materials were used throughout the structure according to their engineering qualities. For example, pumice stone was mixed in with the cement used for vaults. The architecture of the Pantheon rebuilt by Hadrian some 40 years after the Colosseum had some similarities but also introduced innovations of its own.

The arched levels of the Colosseum

The Colosseum has four storeys and each of the first three floors is entirely surrounded on the outside by a series of arches. The visual effect is similar to the series of arches of the aqueducts although the aim here is clearly theatrical and more reminiscent of triumphal arches. Between each arch and the next, there is an ornamental half column which at the ground level is of Doric style, the second Ionic and the third and fourth Corinthian.

The fourth storey doesn’t have any arches but rather a series of square windows which let light into the “cavea” and “arena”. On the outside, the fourth-floor windows alternated with decorative bronze shields which are now gone. The entire building was completely clad in Travertine marble and the surface of it today still shows the holes left by the metal clasps which held the blocks together, and which were later plundered. Some of the original marble slabs are still present in the façade as well as the surrounding paving areas.

Structure of the Colosseum: Entry Gates

Seventy-six numbered entrance gates around the perimeter allowed the public access into the Amphitheatre. The numbering allowed individual spectators to choose the entrance closest to their allotted seat, just like at the Albert Hall in London. The inside of the arches and corridors were covered in elaborate plasterwork. This partly survived through to the Renaissance but only a very small portion is now left. It is not improbable that this plasterwork would have been painted but there is no remaining proof of this. A small area of geometric decoration is still visible in one of the entrance arches.

A plan view of the Roman Colosseum’s structureOther than the standard entry arches there were four main entry gates situated at the two ends and sides. One of these was for the Emperor and high dignitaries, two for the religious processions and one to carry out the dead bodies and corpses. Another formula ascribes two entrances to the emperor and court and two to the gladiators of which one was the small but foreboding Porta Libitinaria through which the piles of corpses were dragged to an unnamed grave.

Corridors and tunnels allowed the spectators access to the internal “cavea” through one of 160 openings called “vomitoria”. From here they could walk along the seat rows to their own allotted place, a little like entering the seating at a Cinema.

Structure of the Colosseum: Seating

Although entry was free all the spectators had numbered seats assigned to them and the seats themselves were divided by social rank and class. The seats of the upper section were made of wood and were reserved for women, the poor, or persons who didn’t have Roman citizenship. Marble seats in the lower levels were reserved for men of Roman citizenship and offered differing levels of comfort according to their social position and rank. Slaves could watch the games standing up in a wooden scaffold built at the very top. Men and Women were not generally allowed to mix. The only place where they could really get up to some “dating” was probably at the Circus.

Other sections of the spectator areas were reserved for special dignitaries such as the emperor or consuls who probably had a reserved box or balcony called “podium” or “suggestum” complete with columns, ivory chairs and other comforts. Pockets of seating areas were reserved for archers who had the task of protecting the public from enraged beasts or fighters which might attempt to jump the protective barrier of elephant tusks and get into the crowd.

The job of the archers wasn’t always clear-cut: It is said that in order to make the show somewhat more exciting Emperor Caligula had a large number of spectators thrown into the arena, instantaneously converting them into actors of the events. But this was an exception.

Structure of the Colosseum: Roof

The top of the theatre had no roof but the spectators were protected from the weather and heat of the sun by covering the Amphitheatre with sails called the “velarium”. A series of posts like short masts, protruded out of the top of the Amphitheatre wall in order to allow the sails to be hoisted and fastened in place. It is probable that the ropes and ties of these sails actually went down to posts which circled the Colosseum at the ground level.

A roman quinquireme shipThe sails alone weighed some 24 tones and two ship’s crews of sailors from Ostia port were required to undertake the sail-roof work. Some accounts suggest as many as 1000 sailors were required for the job. From this height they could also throw water and perfume down for the general comfort of the public and to drown the stench of blood.

Structure of the Colosseum: The “arena” floor and basement

The floor of the arena was made of wood and was covered in sand. In fact, the word “arena” refers directly to the sand (which I seem to recall came from the nearby Monte Mario). Under the arena, there was an 18ft high (6m) basement which stood on cement foundations some 18ft (6m) thick. The basement was about as big as the arena itself. The rooms and corridors of the basement were specially constructed to support the show on the stage above – just like a modern theatre.

The basement rooms were used for a number of purposes such as keeping animals, medics, gladiators, general supplies and so on. It is known that elaborate mechanisms were present to elevate animals and fighters into the arena from the floors underneath so that they could join in the action when it was their turn. Some central ramps allowed larger animals to access the arena. Smaller animals such as lions, for example, could be made to access the arena through a corridor and a number of lateral doors or indeed be hoisted into action through one of 65 small lifts measuring some 2x3ft in aperture. Gladiators could likewise be made to suddenly materialise on stage.

The bottom floors of these buildings could also house other amenities which the spectator public might be interested in such as taverns providing fast food, drink, prostitutes and gambling.

The basement area also had access to a number of underground tunnels which lead to the main Gladiators’ training school called the Ludus Magnus, to the hospital and to the morgue. Mass killings might require the bodies to be pushed out of the arena in stinking heaps through one of the four main doors already mentioned (the Porta Libitina, goddess of corpses) to be carried away to unmarked common graves.

The Colosseum: | Amphitheatres in Ancient Rome| Structure of the Colosseum | The games at the Colosseum | Capital punishment | Organisation of the animal shows | Shows with Wild Beasts | Naval war games Naumachiae | Why the Colosseum? | Gladiators and Christians | Rise and Fall of the Gladiators | Pictures of the Colosseum |