Near Capitoline Hill is a prison that may dates back to the 7th Century BC and King Ancus (640 – 616 BC). At least that is what a Roman historian by the name of Livy (59 BC – 17 AD) suggests. It consisted of two chambers, one above the other.
“The lower room … is known as the “Tullianum” after its builder Servius Tullius (6th Century BC). This part served as a place not of punishment but of detention and execution for condemned criminals. The ancient historian Sallust said it was 12 feet below the ground and “neglect, darkness and stench make it hideous and fearsome to behold.”
The prison was in use until at least the late 4th Century AD, when it was mentioned by the historian Ammianus Marcellinus. After the prison ceased to be used for its original purpose, it became a pilgrim site and accumulated various legends. It later became known as “Mamertinus”.
In the 16th century, the church of San Guiseppe dei Falegnami (i.e., St. Joseph of the Carpenters) was built above the prison.”
The prison was generally regarded as the place to keep high profile prisoners. Traitors to the Empire or those facing execution would be moved here till sentence could be carried out.
The Apostle Peter and the Apostle Paul were most likely held here right around the same time. “Paul may have been detained here before he was executed at the Aquas Salvias (at the Abbazia delle Tre Fontane) and Peter before being executed in Nero’s circus on Vatican Hill.”
It is thought that the Apostles would have been kept in the lower chamber or Tullianum.
If this is correct, than both Paul and Peter would have penned their final epistles from this jail. Peter may even give a hint to their being together in his 2nd letter:
Therefore, beloved, looking forward to these things, be diligent to be found by Him in peace, without spot and blameless; and consider that the longsuffering of our Lord is salvation–as also our beloved brother Paul, according to the wisdom given to him, has written to you, as also in all his epistles, speaking in them of these things, in which are some things hard to understand, which untaught and unstable people twist to their own destruction, as they do also the rest of the Scriptures. You therefore, beloved, since you know this beforehand, beware lest you also fall from your own steadfastness, being led away with the error of the wicked; but grow in the grace and knowledge of our Lord and Savior Jesus Christ. To Him be the glory both now and forever. Amen.
2 Peter 3: 14 – 18
And of course then, Paul would have penned his well-known and well-loved epitaph from the Tullianum:
For I am already being poured out as a drink offering, and the time of my departure is at hand. I have fought the good fight, I have finished the race, I have kept the faith. Finally, there is laid up for me the crown of righteousness, which the Lord, the righteous Judge, will give to me on that Day, and not to me only but also to all who have loved His appearing.
2 Timothy 4: 6 – 8
Church tradition holds that both Apostles were martyred on the same day, June 29th. There may be something to this. The year can fall anywhere from 64 to 68 AD. The Ryrie Study Bible places year at 66 AD. The Archaeological Study Bible places it at 67 AD. H. Wayne House’s Chronological Charts of the New Testament goes with the 64 AD date.
Regardless, Paul was beheaded near the Ostian Way and Peter was crucified upside down on the site where Constantine would later build a basilica dedicated to him (where the Vatican now stands). Nero in all his insanity was the Roman Emperor who ordered their deaths.
Peter chose to be crucified upside down, so as to not be killed in the same fashion as the Lord. Paul, being a Roman citizen (see Acts 22: 25 – 26), was prohibited by law from being crucified.