Krakow: Over a million young Catholics from across the globe are expected to descend on the southern Polish city of Krakow this month for the arrival of Pope Francis at World Youth Day.
"About 600,000 people have already registered, but we expect many more to show up in Krakow at the last minute, so all in all we expect up to 1.5 million people," Monika Chylaszek, a spokesman for Krakow city hall, told AFP.
The US State Department has issued a travel alert, saying huge crowds and extra security should also be expected.
An army of volunteers, some from as far away as Samoa, have been working hard on the event for months, creating a webpage in nine languages, and building a massive altar in a sprawling park in central Krakow.
Brazilian volunteer Fabiola Goulard-Huguelin worked at the last World Youth Day in her native Rio, where she even found love.
"It was a huge experience," she told AFP, adding that she and her new husband decided to volunteer again this year as newlyweds.
Samoan volunteers Martin Leung-Wai and his two sisters Fatima and Ann Margaret have been on the road for months, from New Zealand to Mexico and France visiting Catholic youth missions before arriving in Poland.
Fatima, once an electronics engineer in the oil industry, says she dropped everything to begin the journey.
"If you ask the reason why, it's simple: Jesus", she told AFP. "God sent us on this adventure."
The annual event is this time also a tribute to Krakow's most famous resident, the late Polish-born pope and saint, John Paul II.
He was the city's archbishop before heading to the Vatican – and returned several times during his pontificate.
Pope Francis will visit sites steeped in symbolism, including Czestochowa, Poland's spiritual capital, and Auschwitz-Birkenau.
The pontiff will meet Holocaust survivors at the former Nazi German death camp on 29 July, the third day of his visit to the country.
Two of the pope's predecessors also visited the camp, John Paul II in 1979 and Benedict XVI in 2006.
Some 1.1 million people, including a million Jews from across Europe, were killed by Nazi Germany at the camp from 1940 to 1945. The other victims were mostly non-Jewish Poles, Roma and Soviet prisoners.
Pope Francis will spend five days in Poland, arriving on 27 July and concluding his visit on 31 July.
He will visit the Czestochowa shrine in the country's south and attend a mass there to celebrate the 1050th anniversary of the introduction of Christianity to Poland.
The pontiff will also meet senior Polish officials including President Andrzej Duda in his role as the Vatican's head of state.
This year's World Youth Day will be the 31st edition of the event, initiated in Rome in 1986 by John Paul II. The last was held in Rio de Janeiro in 2013, shortly after Francis' election as pope.