Video from toldinstone
"This video explores some of the ancient and early Christian artifacts hiding in plain sight in St. Peter’s Basilica. For more surprising stories about the city of Rome, check out my forthcoming book "Naked Statues, Fat Gladiators, and War Elephants: Frequently Asked Questions about the Ancient Greeks and Romans" from video introduction.
"Scourging Pillars of Saints Peter and Paul
When in Rome, don't miss the Scourging Pillars. Displayed on each side of the altar of Santa Maria in Traspontina, these partial pillars are said to be those to which Peter and Paul were bound and scourged before they were killed. Located close to St. Peter's Basilica in Vatican City, you can easily see both in one day. The current church structure was built in 1566.
Head of St. John the Baptist
The Bible says that St. John the Baptist, the forerunner to Jesus Christ, was beheaded by King Herod, and Rome's San Sylvestro in Capite claims to have his head. Today, the church displays this crowned head on an altar built by Michelangelo within a gold and silver bejeweled reliquary.
Other churches dispute the head's authenticity and claim they have the true head - although Pope Benedict XVI did tacitly endorse San Sylvestro in Capite's relic's authenticity. " from the article Most Fascinating Christian Relics Around the World
Another good article to read:
Top 10 Relics of Jesus Christ (article link)