Two weeks after the death, cardinals will enter a solemnly secret conclave in the Sistine Chapel, under Michelangelo's awesome fresco of the Last Judgment, to elect the 262nd successor to the apostle Peter. Although the pontiff is the universal leader of more than a billion Catholics, the election will reaffirms the intimate link between the papacy and the eternal city. In the hazy earliest days of Christianity, the pope was the elder or presbyter chosen by the people of Rome, and later by the city's clergy. That principle remains today, with the cardinals - the "hinges" of the church - representing the Roman clergy. No matter where they are in the world, the cardinals are the titular leaders of the churches in or around Rome. Pope Paul VI in 1970 set an upper limit of 120 to the number of cardinals participating in the conclave, all of whom must be under the age of 80. There were 117 eligible electors at last count, representing the broadest range of humanity in the church's history. The election rules were last changed by Pope John Paul II in 1996 with his Apostolic Constitution, or ruling, called Universi Dominici Gregis (All the Lord's Flock). The cardinals will vote up to four times a day in a carefully scripted series of secret ballots. If no-one is elected in the first three days, the cardinals will pause for a day of prayer and then hold another seven votes, followed by another day of prayer. One of the most significant changes introduced by the constitution - intended to prevent a repetition of some of the interminable conclaves of the past - says that if no-one has been elected by a two-thirds majority after about the first 12 days, the cardinals may vote to elect the pope by a simple majority. At this stage, the rules also permit the elimination of all but the two cardinals receiving most votes. As soon as the pope dies, all but three Vatican department heads lose their powers. The cardinal camerlengo or chamberlain, Cardinal Eduardo Martinez Somalo, becomes the temporary head of the church, assisted by three assistants chosen by lot. The pope's vicar or deputy for Rome, Cardinal Camillo Luini also continues in his functions of providing for the pastoral needs of the city. And on the grounds that the doors to foregiveness are never closed, and Vatican "major penitentiary," American Cardinal William Baum, remains in office. During nine days of mourning, Martinez Somalo is responsible for the arrangements for the funeral and burial of the pope and organizing the electoral conclave. The word conclave comes from the Latin "with key." Once the cardinals have entered the precinct, the great bronze door of the apostolic palace is shut to the cry of "Extra Omnes" - all out - and all the doors and windows are closed with lead seals. In the past, the cardinals had to live in spartan quarters in the palace itself, but this time they will stay in hotel-style rooms in a Vatican hostelry called Saint Martha House. The staff assigned to serve them, including confessors, two doctors, cooks and housekeepers, are sworn to secrecy on pain of excommunication from the church. The cardinals also take an oath of secrecy when they enter the conclave knowing that they will be automatically excommunicated if they break it. They are forbidden all contact with the outside world, including newspapers, TV and cell phones. Before the election, the closed precinct is swept for bugging devices. The conclave cannot be held until two weeks after the pope's death to give all the cardinals enough time to reach Rome - a rule reflecting more the age of the horse and carrriage than the jet airliner. Likewise, it must not start later than 20 days after the pope's passing.