The Archbasilica of Saint John Lateran is the seat of the pope - the bishop of Rome. It is the highest-ranked cathedral in all of Catholicism. It even outranks the larger and more famous St. Peter's Basilica. Seeing both St. Peter's and Saint John Lateran Basilicas should be an essential part of any three-day itinerary of Rome.

There is more to the Vatican City than the Vatican City proper, this is the seat of the Pople and it is outside of the Vatican. It is one of the properties of the Catholic church, that enjoys extraterritorial status from Italy - so Italy does not have jurisdiction here. While visiting the Vatican, the best time is with a private early morning tour.