San Giovanni in Laterano is the oldest and ranks first among the four patriarchal churches of Rome; it is the head of all churches throughout Rome and the world. Originally the palace of Constantine, it was later adapted to serve as the church of the Pope. The arch-Basilica was built later on the site of the original church as is known as St. John Lateran or the Lateran Basilica, and is dedicated to St. John the Baptist.

The top of the facade boasts huge statues of Christ and the Apostles. In the five-arched portico, there are as many doors, the last on the right being the Holy Door, which is accessible only every 25 years, during Jubilee years. In July 1993 terrorists damaged it
Inside, huge statues of the Apostles (six on each side) are in niches along the sides of the nave. Along the outside of the church is a loggia where the Pope gives his blessing that is exposed to the elements with beautiful ceiling frescoes. This church has survived two fires. The Papal Altar in this church is reserved for the Pope and only he can celebrate mass from this pulpit. The residence of the Popes until 1309 is also here (The Lateran Palace) and was rebuilt by Domenico Fontana in 1586. In the piazza is an ancient obelisk and parts of Nero's Aqueduct.