The mass is set to take place at 5.30pm that day with the pontiff then set to leave Switzerland from nearby Geneva airport at 8pm.
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Details of the mass have yet to be confirmed. “This has to be organised now with the Vatican,” Palexpo spokesman Claude Membrez told Swiss news agency STA/ATS.
Four of the Palexpo halls are already booked for June 21st but large screens could be placed in the city to ensure more people could follow the mass, Membrez said.
The last papal mass in Switzerland, presided over by Pope John Paul II in Bern in June 2004, attracted 70,000 people but Membrez said the Palexpo convention centre could hold this number or even more.
While in Geneva, Pope Francis will attend a June 21st meeting of the World Council of Churches (WCC) which has some 350 member churches and represents around 500 million Christians globally. The Roman Catholic Church is not a member of the WCC but it does send observers to WCC meetings.
The Pope is then expected to meet with members of the Swiss government.
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The last papal visit to Geneva was in 1984 during a six-day pastoral visit to the country.
A total of 38.2 percent of Swiss people are Roman Catholic while 26.9 percent belong to the mainstream Protestant church, according to official Swiss figures.