Wikipedia: It is the oldest and ranks first among the four Papal Basilicas or major basilicas of Rome (having the cathedra of the Bishop of Rome). It claims the title of ecumenical mother church among Roman Catholics. [...] The cathedral itself is located outside of the Vatican boundaries, within the city of Rome. However it has been granted a special extraterritorial status as one of the properties of the Holy See. This is also the case with several other buildings, after the solving of the Roman Question with the Lateran Treaty.