The Vatican said it was expecting up to one million young people for the vigil, which, together with a Sunday mass, marks the culmination of the week-long youth pilgrimage — a key event in the Catholic Church’s Jubilee holy year.

By Saturday afternoon, the vast open area on the outskirts of Rome — which at over 500,000 square metres was the size of around 70 football fields — was packed by young people. Crowds continued to arrive, music blared over loudspeakers, and a festive atmosphere prevailed.

“I’m so happy to be here, even if I’m a bit far from the pope. I knew what to expect!” British student Andy Hewellyn told AFP.

The massive stage with its golden arch and towering cross was not visible from his seat, but a video screen was nearby.

“The main thing is that we’re all together,” he said, as other young people nearby played guitars, sang, or took a snooze in the sun.

Italian broadcaster Rai dubbed the event a Catholic “Woodstock”, as nearly two dozen musical and dance groups, many of them religious, entertained the crowds ahead of the pope’s arrival.

“The world needs you!” screamed a performer from the stage to the pilgrims who sprawled with blankets, cushions, umbrellas and flags across the dusty area.

Most pilgrims said they planned to spend the night, to attend a final mass Sunday morning led by the pope.

In a video message, Italian Prime Minister Giorgia Meloni welcomed pilgrims to the capital, which she said was “literally invaded by hundreds of thousands of young men and women” who were “praying, singing, joking amongst themselves, celebrating…in an extraordinary party”.

The “Jubilee of Youth”, which began Monday, has seen young pilgrims from more than 146 countries flood the city.

It comes nearly three months after Leo, 69, the first American pontiff, began his papacy, and 25 years after the last such massive youth gathering in Rome under Poland’s Pope John Paul II.

Early Saturday, countless groups of young people set off for the venue in Tor Vergata east of Rome after filling water bottles, applying suncream and adjusting backpacks — ready to spend the next 24 hours surrounded by a crowd of people and then sleep under the stars.

Victoria Perez, who carried a Spanish flag, could not contain her excitement at seeing “the pope up close”.

“It’s the first time I’m going to see him, and I can’t wait,” the 21-year-old told AFP, looking forward to a “night of prayers under the stars”.

French pilgrim Quentin Remaury, 26, said he had been inspired by the late pope Francis’s rousing message to youth during a 2016 visit to Krakow, Poland.

“Pope Francis told us to ‘get off your couches,’ and that really gave me a boost,” he said.

Throughout the week, attendees have participated in various Church-planned events, such as confession at Circus Maximus, one of Rome’s top tourist spots.

On Friday, approximately 1,000 priests were on hand, with 200 white gazebos serving as makeshift confessionals lining the hippodrome where chariot races were once held in Ancient Rome.

The pilgrimage unfolds as under-30s contemplate economic uncertainty and anxiety over climate change.

Samarei Semos, 29, who said she had travelled three days from her native Belize to get to Rome, said she hoped Leo would have a strong say about “third world countries”.

As Parisian student Alice Berry explained: “What does he have to say to us? What is his message for young people?”

The Vatican said the pope on Saturday met and prayed with travellers accompanying an 18-year-old Egyptian pilgrim who died Friday night.

Rai News reported that the young woman died of a heart attack on a bus while returning to her lodging from an event in Rome.