The Vatican closes the Sistine Chapel to the public and prepares for a papal conclave

VATICAN CITY — Exit tourists. Enter cardinals.

The Vatican has closed the Sistine Chapel, where cardinals will gather for the conclave to elect the next pope after the death of Pope Francis on April 21 at age 88.

Francis was buried Saturday after a funeral in St. Peter's Square that gathered world leaders and hundreds of thousands of others, and a nine-day period of mourning is continuing before the conclave can start.

But the church is at the same time turning its attention to the next steps.

Key is preparing the Sistine Chapel for the red-robed cardinals who will gather at the Vatican in the heart of Rome to choose the next pope in an ancient process fictionalized in the 2024 film ''Conclave.''

One key task: installing the chimney where ballots will be burned after votes.

Those visitors who managed to enter on Sunday considered themselves lucky, since there is no telling how long the conclave will last, and how long the gem of the Vatican Museums will remain off-limits.

''I think we felt very lucky to be able to be the last group of visitors to come in today," said Sumon Khan, a tourist from the United States. ''You know, our trip would not have been complete without seeing this beautiful place.''

According to a schedule determined by church law, the conclave can only begin after the nine-day mourning period. It is expected to start between May 5 and May 10.

When it does, the cardinals will enter solemnly to participate in a secretive process said to be guided by the holy spirit that will result in the selection of the next leader of the 1.4 billion-strong Catholic church. The choice will determine whether the next pontiff will continue Francis' reforms, with his focus on the poor and marginalized and the environment, or whether they will choose a pontiff closer in style to conservative predecessors like Benedict XVI focused on doctrine.

For inspiration, the cardinals will also have the great beauty of the frescoes painted by Michelangelo and other renowned Renaissance artists. The most recognizable is Michelangelo's Creation of Adam, showing God's outstretched hand imparting the divine spark of life to the first man.

The chapel is named after Pope Sixtus IV, an art patron who oversaw the construction of the main papal chapel in the 15th century. But it was a later pontiff, Pope Julius II, who commissioned the works by Michelangelo, who painted the ceiling depicting scenes from Genesis from 1508 and 1512 and later returned to paint the Last Judgement on one of the walls.

When the conclave opens, cardinals will chant the Litany of Saints, the solemn, mystical Gregorian chant imploring the intercession of the saints, as they file into the chapel and take an oath of secrecy. The chapel's thick double doors will close and the master of liturgy will utter the Latin words ''Extra omnes,'' meaning ''everyone out.''

The secretive process is part of a tradition aimed at preserving the vote from external interference.

The world will then wait for a sign that a successor to Francis has been chosen. Black smoke coming from the chimney in the Sistine Chapel will indicate that they haven't achieved the two-thirds majority for a new pope.

But when a pope is finally chosen, white smoke will rise and bells will toll.

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Associated Press video reporter Pietro De Cristofaro contributed from Rome.