The basilica of Santa Maria Maggiore is in Rome the largest Marian church in Rome, it is actually located on Italian territory not on Vatican City soil, the basilica hold where the Holy See was consecrated. The Holy See is the headquarters where they foresee the policies and administrate through the Roman Curia. So that the Vatican City operates independently. In simple text is means that they deal with all the diplomatic issues and churches globally. In addition the basilica of Santa Maria Maggiore the Image of the Virgin Mary.