The Cathedral Basilica of SS. Peter and Paul expects more than 3,000 people for seven Masses this week. That means 3,000 Eucharist hosts, 100 poinsettias, dozens of freshly pressed altar linens, and hundreds of hours of staff and volunteer work.

"We started planning last Christmas," said the Rev. Gerald Dennis Gill, the parish rector, who manages daily operations. "This cathedral parish belongs to everybody, and we're invested in preparing it for Christmas."

The cathedral - the largest Catholic church in Pennsylvania - welcomes more people Christmas Eve and Christmas Day than any other holiday on its calendar.

"It truly is a labor of love," said Adam Erdosy, one of three sacristans charged with the handling and positioning of everything needed during a Mass. "Candles must be set, books and linen and the sanctuary must be cleared and made dignified. We want everyone to feel welcome and ready to welcome the Lord."

A three-member maintenance crew keeps the massive Roman-Corinthian structure, with its 201-foot-high dome and 60-foot marble columns, clean.

Maintenance workers Nick Martino and Cecil Velez said the trick is simple: lots of ladders. Martino said Velez is especially good with them.

"He's like a little spider monkey, he grabs on and he can climb here, there, all over," Martino said.

The largest Masses of the year require a lot of laundry.

Margie Silva of Newtown is the cathedral's official launderer. She ran a professional laundry service out of her home for 15 years but has spent the last three months on the bottom floor of the cathedral, where she washes and irons 75 to 100 pieces a week - from priestly vestments to altar drapings.

"I've been scurrying around trying to get everything done," she said. "I do all the altar linens, and some of them feel like they are a mile long."

And she has to follow a special protocol when dealing with the materials used in a Mass.

"Any linen that held the [consecrated Communion host] has to be rinsed, and the water used [must be] poured directly into the ground," she said.

"I just loved laundry," Silva continued. "And you know what I tell people? What I do with the altar linens, everyone else does for humans, but I do for God."

In a modern office building around the corner from the cathedral, Jean Madden, in the Office for Divine Worship, coordinates with the print shop to make sure programs are finished in time.

"They're getting tired down there," Madden said of the printers. Hymns listed in those programs will be performed by the cathedral choir and orchestra, a mix of professionals and volunteers who rehearse each week.

Laura DiPilla, 69, an Italian immigrant who has lived in West Philadelphia since she was 17, is the housekeeper for the rectory.

"We all have biological family at home, but this is our spiritual family," DiPilla said following a staff Christmas party. "And it's a blessing to work here, because when you work here, you go home happy."

Volunteers Louise and Nicholas Pascale - husband and wife who live in Cinnaminson - have penned an 80-page history of the cathedral, which they use to train docents and greeters.

"This place has an incredible history," said Louise Pascale, a retired teacher. "It's a treasure for the city."

Ground was broken for the cathedral in 1846, during James K. Polk's presidency. Amid mounting anti-Catholic sentiment and attacks on homes of Irish Catholics, Bishop Francis Kenrick said the growing denomination needed a larger and more ornate cathedral. When it was first built, all the windows were on upper levels, to prevent vandalism. According to the Pascales' booklet, construction workers threw rocks as high as they could to determine where to place the windows.

The cathedral's designer was a 25-year-old architect, Napoleon LeBrun, who modeled it after the Lombard Church of St. Charles in Rome. LeBrun also designed the Academy of Music, St. Patrick's Catholic Church on 20th Street, and the Metropolitan Life Insurance Co. tower in New York City.

Construction only moved forward as funds were available, according to the Pascales' report, and lasted until 1864.

The cathedral, the seat of the Archdiocese of Philadelphia, has an ornate main altar, eight side chapels, and several shrines. Pope John Paul II visited in 1979 and Pope Francis is expected to visit in September 2015 when he comes to Philadelphia. The staff members will have their hands full again then, when they help organize the Sunday Mass on the Benjamin Franklin Parkway, expected to draw one million people.

On Tuesday evening, as decorators from Flowers by Dante in Southwest Philadelphia put up 10-foot trees, wreaths, and dozens of poinsettia plants, visitors gazed upward at the arches and stained glass. Unlike some cathedrals, Philadelphia's charges no fee to come in and look around, something Gill is proud of.

"I have two goals for this week," he said. "Everyone feels welcome, and everyone knows this is a place where they can encounter the Lord."

Christmas at the Cathedral Basilica

The Cathedral Basilica of SS. Peter and Paul begins its Christmas program Wednesday afternoon. It concludes Thursday.