PITTSBURGH - Christians around the world will observe Ash Wednesday to start off the Lenten season.
Wednesday afternoon, Bishop David Zubik will hold a 12 p.m. mass at Saint Mary of Mercy in downtown Pittsburgh, followed by a 6 p.m. mass at Saint Paul's Cathedral in Oakland.
In the Vatican thousands of people flooded the Vatican's main audience hall Wednesday for Pope Benedict XVI's first public appearance since his bombshell resignation announcement, taking advantage of his second-to-last public audience before retiring at the end of the month.
It's a busy day for Benedict, who will also preside over Ash Wednesday services later in the day to mark the official start of the Catholic Church's solemn Lenten season.
The service is usually held in a church on Rome's Aventine hill, but was moved at the last minute to St. Peter's Basilica.
The Vatican said the shift was made to accommodate the crowds, though it will also spare the 85-year-old pope the usual procession to the church.
Hours before Benedict was due to appear, long lanes snaked out into St. Peter's Square of people waiting to pass through metal detectors to get into the audience hall.
"We were just coming for vacation, and now we are getting all of this!" marveled Terry Rodger, a tourist from New Orleans, Louisiana as he headed to the audience. "I am very excited. I'm surprised."
Benedict announced on Monday that he would retire on Feb. 28, saying he just didn't have the strength of body or mind to carry on.
The Vatican insisted no serious medical ailment was behind the decision, though it admitted for the first time on Tuesday that Benedict has had a pacemaker for years, and recently had it replaced.
The move sets the stage for a conclave by mid-March to elect a new pope. Benedict's final general audience will be held Feb. 27.
He is the first pope to resign in 600 years, and the decision has placed the Vatican in uncharted waters: No one knows what he'll be called or what he'll wear.
The Vatican, however, made it clear that Benedict will play no role in the election of his successor, and once retired, he will be fully retired.
He plans to live a life of prayer in a converted monastery on the far northern edge of the Vatican gardens.
As a result, Benedict's final public appearances are expected to draw great crowds, as they may well represent some of the last public speaking engagements for a man who has spent his life as a priest, cardinal and pope teaching and preaching.
And they will also represent a way for the faithful to say farewell under happier circumstances than when the previous ponotiff, Pope John Paul II, died in 2005.
"It is the perfect occasion to give a cordial and affectionate goodbye to this pope who has given us a great example of courage, humility, inner honesty, and a great love for the church," said Monsignor Claudio Maria Celli, head of the Vatican's communications office.
The Associated Press contributed to this report.