The final event of Sydney's World Youth Day is underway, with Pope Benedict XVI taking the stage before an estimated crowd of up to 500,000 people to celebrate mass.
Today's Papal mass promises to attract the largest crowd ever assembled in Australia, according to WYD organisers.
After the pontiff opened the service with a prayer Sydney Archbishop Cardinal George Pell addressed the faithful.
He said the church was today rejoicing, adding that as he looked upon the "vast congregation" at Randwick it was obvious "the church is alive, and the church is young."
"The church ... proclaims the Lord Jesus and she has no other task, no other agenda, no other mission," he said.
"Yet as she makes her way through history, in the ancient lands of the Mediterranean or the new frontiers of the Pacific, it can be difficult to see the church as she truly is.
"Too often she is weighed down and burdened with the sins and failings of her children, too often she appears disfigured and discouraged."
Dr Pell said he gave thanks for WYD, which was a gift for the church as a whole.
"At World Youth Day the church appears as she truly is, alive with evangelical energy," he said.
"This morning in Sydney, we see the church not only with the eyes of faith, but manifest before us."
The pontiff had a bird's eye view of the enormous crowd when he flew over Royal Randwick Racecourse in a helicopter this morning.
Around 235,000 young Catholics had joined him in a vigil at the venue last night, having lugged sleeping bags and blankets on a nine kilometre pilgrimage.
They spent the night sleeping under the stars, eagerly awaiting today's mass, and were joined by tens of thousands more people this morning.
The Pope did a lap of the racecourse in his Popemobile this morning after a brief pass through a section Centennial Park.
As the motorcade neared its end, a baby was passed to the Holy Father, who kissed and blessed the child.
