The likes of St. Peter were martyred by Nero “inter duem metam”. The “metae” were the pyramidal posts at the ends of the Circus track but which circus? The best bet is Nero’s Circus on the Vatican hill.
The early Christians, at the time of Emperor Nero saw martyrdom at the circus; the Colosseum was not even built at that time. Saint Paul, being a Roman citizen, was beheaded not crucified. The execution was by the Ostian road, in a location now known as “the three fountains” because his head is said to have bounced three times and given rise to springs.
St. Peter who was at Rome with Paul, was probably martyred at Nero’s circus, on the Vatican Hill. As he was not a Roman citizen St. Peter was crucified upside down, “inter duem metam”: The “metae” were the pyramidal posts at the two ends of the Circus track and hence there are several interpretations as to where the Saint was actually crucified.
On the Vatican Hill which seems to have been a frequent site for crucifixion
or indeed between two Pyramids which were in Rome at the time
Nero’s circus was in fact started by Emperor Caligula and finished by Claudius. The Circus’ location by the major roman roads of Via Triumphalis and the Via Cornelia meant there were many tombs in that area already. Now we can see there is a Roman graveyard about 2 acres in size which was started around the 1st century BC, hence pagan, and closed around 320 AD with a mixture of pagan and Christian. Many of these were also anonymous graves created during Nero’s persecution of the Christians.
Emperor Constantine later started St.Peter’s basilica over part of the circus, literally covering the site of the executions and the graveyard.
Why were Christians publicly executed in the Circuses and Amphitheatres?
The public games and executions were violent displays where criminals and anything anti-Roman was a counterpoise to “Romanity”. The Christians in their unambiguous following for one Lord, Jesus Christ, and their refusal to pay homage to the Roman gods and to the Emperor-Divinity made them traitors.
It was customary to execute criminals, particularly non-citizens, who had been given the death penalty at the Ludi: public games and entertainment.
Christianity brought the Circus and Colosseum to an end
The Christians and their new view of morality actively and publicly contrasted the games at the Colosseum. This was because of the violence within them, but also their role as pagan religious sacrificial function. It was not an easy transition for society to accept: In one event a monk broke into the arena to proclaim his disgust and was duly stoned to death by the crowd. It is possible that events such as these forced the end of the games around the fifth century (404AD) during the reign of Emperor Honorius although games with beasts went on for a further century.
During the Middle Ages the Christians converted the Colosseum to a sort of martyrdom memorial. Now there is some doubt over the actual number and possible over-estimation of martyrs who actually died there.
The Colosseum was increasingly used as a stage for a number of religious displays which with the passing of time were supplemented with increasingly profane exhibitions. All shows were eventually abolished during the Renaissance. The cross which still stands in the Colosseum dates back to the 18th century.