Ecclesiastical Basilicas
The Early Christian purpose-built basilica was the cathedral basilica of the bishop, on the model of the semi-public secular basilicas, and its growth in size and importance signalled the gradual transfer of civic power into episcopal hands, which was under way in the 5th century. Basilicas in this sense are divided into classes, the major ("greater") basilicas and the minor basilicas; there are three other papal and several pontifical minor basilicas in Italy, and over 1,400 lesser basilicas around the world.
Churches designated as papal basilicas, in particular, possess a papal throne and a papal high altar, at which no one may celebrate Mass without the pope's permission.
Numerous basilicas are notable shrines, often even receiving significant pilgrimages, especially among the many that were built above a confessio or the burial place of a martyr – although this term now usually designates a space before the high altar that is sunk lower than the main floor level (as in the case in St Peter's and St John Lateran in Rome) and that offer more immediate access to the burial places below.
Read more about this topic: Basilica