At the Cathedral Basilica of Saints Peter and Paul in the center of Philadelphia, the atmosphere is calm. Thickly scented incense smoke rises slowly, caught in the streams of sunlight piercing through the cathedral's strained glass windows. But even as the weekly mass takes place, there is a flurry of activity and excitement as this community gets ready to welcome Pope Francis, the head of the Catholic Church. For months now, the city has been gearing up for the visit, and as the big day gets closer, the clergy are keen to reassure the congregation that the event will run smoothly.

"To those whose hearts are frightened: Fear not," says Father Ken Brabazon, addressing his parishioners, around 200 of whom have turned out for regular Sunday mass in the largest church in the state of Pennsylvania. He's referring to the panic that arose when the organizers of the pope's visit announced, just a few weeks before the event, that anyone wishing to be within five blocks of the pope when he conducts mass on Philadelphia's main highway would have to get a ticket.

The tickets are free, but there are a limited number - the 10,000 made available for various events were snapped up within minutes. Soon afterwards some tickets were being sold online for hundreds of dollars a piece.

Mass for the masses

Father Ken, a young priest who rocks forward onto his tiptoes to make his point, has no need to worry. It's here in this cathedral that the pope will hold a special mass for select members of the clergy. But for almost two million parishioners and pilgrims hoping to see the Holy Father, it will be a less intimate affair - a huge outdoor mass, set to take place on Benjamin Franklin Parkway, the largest street in the city.

"It's probably going to be packed, but I do want to come and see him," says Katerina Kelekolio, a Philadelphia local attending the Spanish-language mass, taking place in the chapel which is part of the Basilica. "When I found out about the tickets I was kind of mad, but as long as I get to see him I'll be happy." Catholics believe the pope is Jesus Christ's representative on Earth, so the chance to get close to him is something special.

Latinos strengthen Catholic church

It's a mixed crowd, and many of the congregation have come here alone. A bearded man with a mermaid tattoo on his right forearm shares a wooden pew with a woman in her Sunday best, with high heels and an expert blow dry. Fewer are attending the Spanish-language mass, but more of them have brought their children along, and the sound of murmuring and good-natured fidgeting mingles with the liturgy recited in Spanish - the mother tongue of the Argentine Pope Francis, who is expected to speak it during most of his trip.

It's an important sign of recognition for the Spanish-speaking Catholic population. According to research from Georgetown University, Latinos make up about 38 percent of Catholic adults in the US, and are boosting the number of Catholics in the country even as a steady stream of Americans are leaving the faith.

Olympic-scale event

Catholics from all over the world are travelling to Philadelphia for the pope's visit, which will coincide with the World Meeting of Families, a huge gathering of Catholic families held every three years. There have been concerns over whether the city can cope with the influx of pilgrims expected. Major roads are set to close for more than two days and the city center has been declared a traffic-free zone for the event. Some Philadelphians are worried that restrictions within the city will affect businesses, essential deliveries and those trying to get to work. The pope's visit has even been designated a "national special security event," the same status given by security services to events like the Olympic Games.

But authorities hope the logistical challenge will be worth it. With hotels in the region close to capacity, the upcoming explosion of faith-based tourism is expected to generate hundreds of millions of dollars in revenue. "This is an accomplishment for our city rather than a drawback," says Edward Brittingham, a lawyer reading the Sunday papers on a park bench close to the cathedral. "I'm not religious, but I might want to take a peek out of curiosity."

For others it's an opportunity. "I'll get some overtime," says Herb Baskerville, a municipal worker clearing litter from the park's green lawns. "It's a great thing for the city."

'It's a blessing'

After the mass, churchgoers stream out of the cathedral into the hot sunshine. Ryan Nguyen, a 33-year-old trainee priest in a freshly ironed shirt, hopes the excitement around the pope's visit will encourage more young people to embrace Catholicism. "Hopefully this will reinvigorate the whole church," he says. "I'm just starting seminary so I think it will give me an extra boost for the next seven years. It's perfect timing!"

The rest of the parish shares his sense of anticipation about seeing the pontiff. "It's history, it's so exciting to be a part of it," says Chelsea Crawford, who has come from the suburbs to get a sense of the atmosphere. "Just to have him close to our community and have his presence close to us, it's going to be such a gift."