It's not often, in our secular age, that you see a place of such intense, passionate devotion, but this tells you something about Rome as a holy city. A holy city is a place where God meets man. And that is exactly what these pilgrims are doing. While Helena was importing holiness from Jerusalem, Constantine was keen to promote the city's home-grown Christian sites. But he had to be careful. Rome was still overwhelmingly pagan, and that's why he built his first churches away from the centre. Constantine built seven churches in Rome. But one took on supreme importance. Nero's Circus had become a holy place for Rome's Christians, as the location of Peter's crucifixion and burial. A simple shrine had been erected over his grave. Constantine recognised the importance of the site. A direct link between Rome and Jesus Christ himself, through his right-hand man, Peter. So Constantine decided to build his biggest basilica over Peter's tomb.