Isolated from the outside world, 133 cardinals gather in the Sistine Chapel.

A new pope will be elected in the Vatican starting this Wednesday. Two and a half weeks after the death of Pope Francis, 133 cardinals from around the world will gather in the Sistine Chapel, closed to the outside world, to decide on his successor. The first round of voting will take place this afternoon. A decision is not yet expected.

A two-thirds majority is required to elect the pontiff—the 267th pope in two millennia of church history. There are 1.4 billion Catholics worldwide. The media and bookmakers are tipping the favorite to be the current number two of the Catholic Papal States, Cardinal Secretary of State Pietro Parolin. As the highest-ranking cardinal, the 70-year-old will also preside over the conclave. Three cardinals are from Germany.

Before the conclave, the church leaders gather in the morning for a large mass in St. Peter's Basilica. Cardinals 80 years of age and older are also present. Afterward, the other 133 are alone. After a lunch break, they go to the Sistine Chapel – one of the most beautiful polling stations in the world. There, the cardinals must swear an oath to God that they will observe the ban on contact and secrecy. They must surrender their cell phones, smartphones, and all other digital devices.

The first round of voting will take place this afternoon – and then, in all likelihood, black smoke will rise from the chimney of the Sistine Chapel in the early evening. No one expects a new pontiff to be elected immediately. Only with a two-thirds majority – that is, at least 89 votes – will the smoke be white. That could take some time. Once that happens, the announcement will be made from the balcony of St. Peter's Basilica: Habemus Papam (We have a Pope). Then the new head of the church will appear to the public.

No one knows how long we'll have to wait for this moment. Since the 1960s, the conclaves have always lasted only two or three days. This time, however, quite a few are expecting a longer period. German Cardinal Gerhard Ludwig Müller (77) told the German Press Agency that he had his suitcase packed for "five or six days." "You have to be prepared. But everyone hopes, of course, that it won't take that long. Everyone wants to go home."

Also participating from Germany are Cardinals Reinhard Marx (71) from Munich and Rainer Maria Woelki (68) from Cologne. The likelihood of a German pope again 20 years after the election of Benedict XVI is slim. However, the well-connected Marx is being touted in the Italian press as one of the potential "kingmakers"—that is, someone who can steer the conclave toward a particular candidate.

The list of possible successors to Francis has been growing longer by the day. In addition to Parolin, two other Italians are considered candidates: the Archbishop of Bologna, Matteo Zuppi (69), and the Patriarch of Jerusalem, Pierbattista Pizzaballa (60). Also in the candidate carousel are the Filipino Luis Antonio Tagle (67), the Frenchman Jean-Marc-Aveline (66), the Portuguese José Tolentino de Mendonça (59), the Hungarian Peter Erdö (72), the Luxembourger Jean-Claude Hollerich (66) – and several more.

If, as expected, no agreement is reached in the first round, elections will be held twice in the morning and twice in the afternoon until the matter is decided. Most Vatican experts expect this to happen this week. The Argentinian Jorge Mario Bergoglio, who later took the papal name Francis, was elected in 2013 after a day and a half, in the fifth round of voting. He led the Catholic world church until his death on Easter Monday at the age of 88.

According to Catholic doctrine, the Pope is the successor of the Apostle Peter and the vicar of Jesus Christ on earth. He is also the Bishop of Rome, Primate of Italy, and Head of State of the Vatican. He does not wield great worldly power. However, for many people, he is a moral authority. Francis has repeatedly spoken out on current issues. He has not shied away from criticizing those in power.

Unlike his immediate predecessors, the Argentinian renounced many privileges and status symbols. He was buried not in St. Peter's Basilica in the Vatican, but in the Church of Santa Maria Maggiore near the main train station—his favorite church in Rome.