The design and construction of the first permanent stone amphitheatre in Rome was innovative and set the standard for amphitheatres across the Roman Empire.
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 nature of the 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. 2 brick walls were built with concrete sandwiched in between. 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 which acted as the initial supports for the seating area were held in place by a bed of powdered travertine mortar which was 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 was also used to face 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 4 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 level after that.
The fourth level consisted of rectangular columns known as Corinthian piliasters. These columns divided the final level into 80 compartments, each with a small opening. It was in these ‘rooms’ that contained the series of beams for controlling the velarium or awning that shaded the audience from rain or sun.
The seating of the Colosseum was divided into five levels or maenianum. Seating in 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 subsellia was a special area of seating within the ima cavea reserved for senators.
Next came the maenianum primum. Consisting of 8-9 terraces, this was the area where the equites or knights sat.
The maenianum secundum imum and maenianum secundum summum consisted of .19-20 terraces for the ordinary citizens. At peak 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, as well as 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 would then be guided to their seating area via a series of corridors specific to their entrance.
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 the Emperor Domitian. This basement area also housed the arena’s service quarters where scenery was stored and hoisted upwards for spectacles.
The gladiators did not have quarters under the Colosseum. Rather, 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.
The Colosseum: The Official Guide. Electa: Soprintendenza Archeologica di Roma
Connolly, P , (2003). Colosseum: Rome’s Arena of Death . BBC Books.