ANSWER: The Bible clearly states that Peter would die a Christian martyr but does not state it would be in Rome. Jesus, shortly after his resurrection, revealed to the apostle that he would give his life for the sake of the gospel. John recorded Christ stating, "'Truly, truly I say to you . . . when you are old, you shall stretch out your hands, and another shall dress you . . .' Now He said this to signify by what death he (Peter) would glorify God . . ." (John 21:18 - 19, HBFV).
Many Bible commentaries believe, based on tradition, that Peter likely died in the city of Rome under Nero's persecutions (just like the apostle Paul). Others, like the Roman Catholic Church, dogmatically declare that such a supposition is true. They state, in their 1913 Catholic Encyclopedia regarding the apostle, "It is an indisputably established historical fact that St. Peter labored in Rome during the last portion of his life, and there ended his earthly course by martyrdom."
There are some commentaries, however, that openly state Peter may have never "the eternal city," let alone died in the city. According to the "Complete Book of Who's Who in the Bible," there is no definitive Biblical evidence that he ever visited Rome. The ISBE states, in their article on the apostle, "It should be observed, however, that the tradition that he visited Rome IS ONLY TRADITION AND NOTHING MORE . . .". What is abundantly clear is that John 21 does not state the apostle's martyrdom would be in the city.
The New Testament offers evidence that, even if Peter had somehow made it to Rome, he did not stay long in the city before he died. The apostle Paul wrote the book of Romans in the winter of 57 A.D. The book does not mention him at all, which would be an incredible oversight if he had lived in and evangelized the city.
More importantly, Paul told believers in Rome, in the book of Romans, that his policy was to evangelize in places (like where they lived) where no one had previously carried out such efforts (Romans 15:20, see also 2Corinthians 10:15 - 16). It is almost certain that Peter did not visit or preach in the city prior to 57 A.D.
Paul, at the end of his fourth missionary journey, lived in Rome from 61 to 63 A.D. During his time in the city, he wrote the books of Ephesians, Philippians, Colossians, and Philemon. Again, he makes no mention of Peter, which would be a glaring omission if he were also a prisoner in the famed city. Although this is not conclusive proof, it suggests Simon did not preach or live in the city before 63 A.D.
Some believe that Peter wrote his first epistle from Rome (written between 64 and 65 A.D.). This belief is based on the argument that he used symbolic language to refer to the eternal city and not to the literal city of Babylon (1Peter 5:13). Part of the argument in rejecting his referral to the literal city is the belief that there would be no reason for him to go there. In-depth research, however, shows otherwise! Parthians (from Babylon) were among the many Jews in Jerusalem, on Pentecost in 30 A.D., who heard the gospel preached (Acts 2:9).
The book "Lost Ten Tribes of Israel FOUND!" pages 310 - 311, states, "Josephus and Jesus Christ did not consider the ten tribes to be 'lost' at all, but rather living in known geographical locations. It is significant that the Apostle Peter wrote the book of 1Peter from the city of Babylon . . . Since Babylon was a city of the Parthian Empire at that time, it indicates that Peter had heeded Jesus Christ's instructions by traveling to territory ruled by the ten tribes"
Peter wrote his second and final letter between 65 and 66 A.D. In it, he does not mention he was in or was writing from Rome. Since he likely died between 67 and 68, any possible visit to the city would have been quite short and offered little time to spread the gospel before he was to die. There does exist, however, the possibility that Peter never visited the capital city and suffered as a martyr somewhere else!