The correct answer is option 1: Rome. St. Paul, who was an apostle and played a significant role in spreading Christianity, was beheaded in Rome. Rome was the center of the Roman Empire at that time, and it was where many Christians faced persecution. St. Paul was tried and condemned to death under the Emperor Nero during the first century AD. He was executed by beheading, as was a common method of execution during that time. This event is significant in Christian history as it marked the martyrdom of one of the most influential figures in the early Christian movement. It is important to note that while St. Paul had traveled to other cities during his ministry, he was ultimately executed in Rome.