How did Saint Peter die?

According to Tradition

The Bible does not record Peter's death. Tradition indicate that Peter was crucified upside-down, as he said that he did not deserve to die in the same manner as his Master (Jesus).
 

Answer

The Bible never mentions Simon Peter's death. Acts of the Apostles mentions the imprisonment and miraculous release of Peter, but does not say anything about his subsequent death, even though the book was written around the end of the century, long after Peter would have died.

However, the mid-second century pope Anicetus (156-166) said that Peter was beheaded by Nero in Rome. The reason for this claim was that he had became locked in a conflict with Polycarp of Smyrna. Polycarp had tried to win the argument by insisting that he spoke with the authority of the apostle John. In response, Anicetus told of Peter's beheading and said that he spoke with the authority of Peter. Then in the third century, the Church Father Origen changed the story somewhat, saying that Peter, condemned to crucifixion, felt himself unworthy to be crucified the same way as his Lord, and so chose crucifixion upside down.

In fact, we do not know how or where Simon Peter died.
 

Answer

See discussion. According to Catholic Encyclopedia and George Edmundson of Oxford University (a recognized early Christian historian), Peter died in Rome and most probably by cruxifition. For instance, Tertullian around 200 clearly states Peter died by cruxifition under the Nero persecution.