Liberato De Caro (National Research Council), Fernando La Greca (Salerno University), and Emilio Matricciani (Milan Polytechnic) published a study in the peer reviewed MDPI.com entitled: "The search for St Peter's memory 'ad catacumbas' in the cemeterial area 'ad Duos [sic!] Lauros' in Rome."
Their thesis: Saint Peter is buried in Torpignattara, Rome, in the large and partly unexplored catacombs "Ad Duas Lauros," underneath Santi Marcellino e Pietro ad Duas Lauros church (not to be confused with Santi Marcellino e Pietro al Laterano).
Around 330, Emperor Constantine built a Mausoleum for himself and his mother Helena which is now attached to the church of Saints Marcellinus and Peter, allegedly two minor 4th century martyrs. But according to the article, in ancient times the order of the names was “Peter and Marcellinus.” Peter meant the apostle.
The hypothesis is that St Peter’s remains were moved from the Vatican Basilica to Torpignattara because of the persecutions and the barbarians. Therefore, in 354, the commemoration of St Peter was celebrated in Torpignattara, not at the Vatican.
The article mentions that in the catacombs, a significant 4th century sepulchral epigraph on Peter and a fresco depicting him holding a scroll were found. The authors believe they have identified the still unexplored crypt with his tomb.
They write that Pius XII (+1958) once asked the famous mystical writer Maria Valtorta (+1961) about St Peter’s tomb. Valtorta replied that she saw it in a vision in Torpignattara containing St Peter’s mummified remains holding an ancient parchment. Valtorta allegedly also described the crypt.
Picture: Chiesa dei Santi Marcellino e Pietro ad Duas Lauros © wikicommons, CC BY-SA, #newsOlyaqjyebd