The head church of the Roman Catholic Archdiocese of Philadelphia, Cathedral Basilica of Saints Peter and Paul was built from 1846-1864. The cathedral has been the site of two papal Masses, one celebrated by Pope John Paul II in 1979, and the other by Pope Francis in 2015. With its grand facade, vaulted dome, ornate main altar, eight side chapels and main sanctuary that comfortably holds 2,000 worshippers, the cathedral is the largest brownstone structure and one of the most architecturally notable structures in the city of Philadelphia. The cathedral is the largest Catholic church in Pennsylvania, and was added to the National Register of Historic Places in 1971.