Which of the twelve apostles of Jesus Christ was crucified on the cross upside down?

According to Christian tradition, Peter was crucified in Rome under Emperor Nero Augustus Caesar. It is traditionally held that he was crucified upside down at his own request, since he saw himself unworthy to be crucified in the same way as Jesus. Tradition holds that he was crucified at the site of the Clementine Chapel. His remains are said to be those contained in the underground Confessio of St. Peter's Basilica, where Pope Paul VI announced in 1968 the excavated discovery of a first-century Roman cemetery. Every 29 June since 1736, a statue of Saint Peter in St. Peter's Basilica is adorned with papal tiara, ring of the fisherman, and papal vestments, as part of the celebration of the Feast of Saints Peter and Paul. According to Catholic doctrine, the direct papal successor to Saint Peter is the incumbent pope, currently Pope Francis.