The second and third of the principal concentric walls contain arches corresponding to those in the outer wall. Corridors run between these concentric walls, and on the first and second floors of the outer ring, and the first floor of the inner ring, these circles afford a completely unobstructed passage all round. The other corridors are blocked up in parts by various staircases, leading to the upper rows of seats.

Within the third principal concentric arcade the supports of the building take the form of massive walls, radiating from the centre of the ellipse, and divided by elliptical corridors into three ranges. Between these massive walls and in the corridors are the steps and passages leading to the lower seats of the amphitheatre. The actual seats which were of marble have been all pilfered for the benefit of the Roman palaces and churches of the feudal ages, but we can still make out with tolerable certainty the five principal divisions into which they were separated. The lowest of these, called the podium, was a platform raised twelve or fifteen feet above the arena, upon which were placed the chairs of the higher magistrates and dignitaries. This was protected by railings and nets full of spikes, and sometimes also by trenches, called euripi, and horizontal bars of wood or iron which turned freely round, and thus afforded no hold to the paws of a wild animal.

Above the podium were four different orders of seats, divided by belts of upright masonry from each other. The first of these consisted of about twenty rows of seats, and was appropriated to the knights and tribunes, and other state officers. The upper row of this set was probably at a height of about ten feet above the top of the arches of the lowest story. The next ranges of seats between the second and third belt were appropriated to Roman citizens in general, and held the greatest number of spectators.

The wall dividing these seats from the next set was very high, and contained, besides the vomitoria or entrance doors, a number of windows for the purpose of lighting the corridors and passages. A considerable part of this wall is still extant upon the side towards the Esquiline Hill. Above it ran the third set of seats, occupied by the lower classes of the people, and above this again, and separated from it by a very low wall without vomitoria, was the fourth group of seats, immediately under the windows of the uppermost story, and covered by a portico which ran round the whole top of the building.[71] The traces of this uppermost row of seats and of the colonnade which supported the portico may still be seen on the side towards the Esquiline Hill.

The seats in this part seem to have been partly appropriated to women, partly to the lower classes. On the roof of the portico stood the workmen whose business it was to manage the awnings, and to move them as the sun or rain required. The number of seats in the whole amphitheatre is said to have been 87,000, and a considerable number, in addition to these, could stand in the passages between the seats at the entrances of the vomitoria, and in other vacant places, so that the whole number which the building, when filled from top to bottom, could hold, was probably not less than 90,000.

The exterior arcade of the building diminishes in thickness towards the top, in order to render it more stable, and while the Doric and Ionic columns of the first and second stories stand out from the wall by nearly three-quarters of their circumference, the third row of Corinthian columns projects less, and the uppermost row are merely pilasters.

Much discussion has been raised on the question of the awnings or velaria required for so large a space. It is impossible of course, in the absence of any distinct contemporaneous description, to discover the exact mode of suspension adopted. Venuti supposes that a net of cords constructed like a spider’s web, with both radiating and concentric ropes, was suspended over the amphitheatre, and that by pulleys arranged over this the vela were drawn across any part which happened to be exposed to the sun. By means of pulleys attached to this network of rope, the little boys mentioned by Juvenal as caught up to the awnings may have been drawn up. The ropes and pulleys, we are told by Lampridius, were managed by sailors. In rough and windy weather the awnings could not always be drawn, and umbrellas coloured according to the favourite’s colours, or large broad-brimmed hats called causiæ or birri, were then used. Martial has written some amusing epigrams, showing how jealously the seats appropriated to any particular privileged order were reserved. He gives the names of Lectius and Oceanus to the boxkeepers of his time, who chased intruders from the seats to which they were not entitled. And he describes with great humour the attempts of a certain Nanneius to smuggle himself into a better place than he was entitled to. The pickpockets of Martial’s time also frequented the amphitheatre.

The anxiety of the public to attend the shows was so great that they occupied the free seats in the amphitheatre before dawn in the morning, and gave fees to the officials to keep places for them, when any favourite gladiator or bestiarius was announced to perform. The shows lasted whole days, and hence various contrivances for keeping the spectators in good humour, and filling up the intervals between the combats. Seneca tells us of the meridiani, a class of slaves who were kept on purpose to fill up the midday leisure hours with sham fights, and ludicrous pranks played upon the bodies of those killed or half killed in the previous fights. The air was cooled with immense jets of water projected from the centre of the arena, or from holes in the statues, and scented with fragrant essences, among which extract of saffron mixed with wine seems to have been the most popular.

The arena of the Coliseum was originally about 250 feet in length, and 150 feet in breadth. It seems now much larger on account of the removal of the wall of the podium. The attention which has been drawn to the arena during the last few years by the re-opening of the hypogæa, or subterranean passages, renders it necessary to allude to the subject of these hypogæa, and to estimate how far the recent excavations have thrown new light upon the history and construction of the great amphitheatre. When the French occupied Rome, and it was incorporated into their empire in the four years preceding the Battle of Waterloo, the French Government carried out considerable excavations in the arena of the Coliseum, and besides clearing the podium and the chambers annexed to it, they opened the cryptoporticus which runs underground towards the Cælian Hill, and also discovered the passages beneath the arena which have been now excavated again.

A great controversy was raised at that time as to the real level of the original arena between several of the archæological professors and antiquarians of Rome. The same controversy has now been again revived, and the same questions as to the probable date of the underground constructions have been again raised, but with as little hope as ever of arriving at a satisfactory solution. The truth seems to be that, as in most amphitheatres, these hypogæa were constructed at the very first erection of the Coliseum, but have been altered, neglected, filled up, and again cleared out many times during the eventful history of the building, and that it has now become impossible to trace the various stages of such destructions and restorations. As often as the drains which were intended to carry off the water became choked and failed to act, these lower chambers and passages were filled with water and rendered useless.