Final answer:
Saul, known as Paul post-conversion, hailed from a city likely practicing Hellenistic and Roman pagan religions. His conversion marked a shift to Christianity, which he spread throughout the Greco-Roman world.
Step-by-step explanation:
The city where Saul, later known as Paul after his conversion to Christianity, was born is not explicitly mentioned in the question. However, from historical accounts, we know that Paul was originally a Jew from Tarsus and was a Roman citizen. His birthplace possibly practiced a mix of Hellenistic and Roman pagan religions. Tarsus was a city known for its diverse religious and cultural practices due to its location within the Roman Empire.
After Saul's conversion, his beliefs drastically shifted to the monotheistic Christian faith, and he became a crucial figure in the spread of Christianity throughout the Greco-Roman world, including in cities like Ephesus, Corinth, Thessalonica, and Rome.
The growth of Christianity, with its roots in Jewish belief in one God, stood in contrast to the polytheistic traditions of the Roman Empire, which sometimes resulted in the persecution of Christians for challenging state religious authority. Saul's conversion experience and subsequent evangelism were pivotal to the development and spread of Christian beliefs in the ancient world.