It is generally accepted that Peter was crucified upside down in Rome.  Tertullian and Origen attest to this.

From [WikiPedia][1]:
> According to the 1911 Catholic Encyclopedia, St. Peter labored in Rome
> during the last portion of his life, and there ended his life by
> martyrdom.[17] The death of St. Peter is attested to by Tertullian at
> the end of the 2nd century, and by Origen in Eusebius, Church History
> III.1. Origen says: "Peter was crucified at Rome with his head
> downwards, as he himself had desired to suffer."[17] This is why an
> upside down cross is generally accepted as a symbol of Peter, who
> would not have considered himself worthy enough to die the same way as
> his Savior.[35]

Whether or not [Peter](http://en.wikipedia.org/wiki/Saint_Peter#Connection_to_Rome) was bishop of Rome is still debated, although it is a belief held by the Catholic church. 

  [1]: http://en.wikipedia.org/wiki/Saint_Peter#Death