The design of the Colosseum was unique. At 52m high, covering 3357 square metres, and with a capacity to seat 73,000 people, it was the largest and most complex amphitheatre in the Roman world. No other amphitheatre eclipsed it.

Laying the Foundations

Because of the marshy terrain the Colosseum occupied, the foundations made full use of Roman engineering to support its massive structure.

The structure was to occupy the drained basin of the lake to Nero’s Golden House. Engineers dug 6m below the bottom of the lake and then a further 4m into the clay subsoil until they had an oval-shaped ditch, 50m wide and 200m long.

The ditch was then lined with brick and concrete facings. In all, the facings were 3m thick and 6.5m high. The concrete was poured to what had been the level of the lake bed.

The foundations were then constructed. They consisted of four travertine stone tunnels and a series of concrete vaults that ran under what would be the arena and seating areas. The travertine blocks that acted as the seating area’s initial supports were held in place by a bed of powdered travertine mortar laid over the concrete.

What was the Colosseum Built From?

The main walls of the Colosseum were built from travertine stone, a hard white limestone quarried in Tivoli, 35km from Rome. Inside, the radial walls were constructed from brown volcanic tufa, mined from the old city walls. The tufa was faced with plaster and painted in a variety of colours. The initial colour scheme was quite bright, with internal passageways painted black, yellow or red.

Marble faced the cavea or seating areas and some of the lower flooring. The upper floors were covered with opus spicatum, a herringbone pattern of brickwork.

The Walls of the Colosseum

The upper structure of the Colosseum consisted of four levels. The first three levels consisted of 80 arcades framed by various orders of columns. Those on the ground level consisted of half Doric columns, with Ionic columns on the next level and Corinthian on the next level. 

The fourth level consisted of rectangular columns known as Corinthian pilasters. These columns divided the final level into 80 compartments, each with a small opening. These “rooms” contained the beams for controlling the velarium or awning that shaded the audience from rain or sun.

The Seating.

The seating of the Colosseum divided into five levels or maenianum. Seating at each level was reserved for a specific social group in accord with the legislation of Augustus, which strictly segregated not only different social classes but also men and women.

The Ima cavea was the level nearest the arena. It was reserved for VIPs such as magistrates, priests and foreign diplomats (hospites). The subsellium was a special seating area within the ima cavea reserved for senators.

Next came the maenianum primum. Consisting of eight to nine terraces, this was the area where the equites or knights sat.

The maenianum secundum imum and maenianum secundum summum consisted of 19 to 20 terraces for ordinary citizens. At the pinnacle of the amphitheatre was the maenianum secundum in ligneis or the attic. This consisted of 10-11 terraces of wooden seating, which gave it its name. This was the area where the lowest classes, slaves and women sat.

Admission to the different seating areas was carefully controlled, with each group admitted according to the information on their ticket. Each ticket would stipulate which entrance they should take and the section and row number they should sit in. The entrance numbers are still clearly visible on the north side of the Colosseum today. The spectators were guided to their seating area via a series of corridors specific to their entrance.

The Arena

The arena floor was wooden and covered with sand. It was entered from the basement of the Colosseum by stairways completed during the era of Emperor Domitian. This basement area also housed the arena’s service quarters, where the scenery was stored and hoisted upwards for spectacles.

The gladiators did not have quarters under the Colosseum. Instead, they were housed at the nearby ludus magnus or gladiator barracks. They made their way to the basement via an underground corridor situated to the east, which connected the two buildings.

Resources

The Colosseum: The Official Guide. Electa: Soprintendenza Archeologica di Roma

Connolly, P, (2003). Colosseum: Rome’s Arena of Death. BBC Books