Pilgrims sang, cried and dropped to their knees to pray on the cobblestones of St. Peter's Square (search) on Monday as cardinals held their final Mass before shutting themselves inside the Sistine Chapel (search) to elect a new pope.

Thousands of people passed through metal detectors to get into St. Peter's Basilica for the midmorning Mass celebrated by the 115 crimson-robed cardinals who will elect the successor to John Paul II (search), while thousands more followed the service on giant screens in the square.

Rwandan nuns in blue habits, Filipino monks in gray robes and tourists in T-shirts mixed together, shaking hands and hugging in the sign of peace. Tears streamed down the faces of Leila Mota and Mariana Dias as they embraced tightly.

"For the rest of my life, I'll keep this moment in my heart," said Dias, a 27-year-old architect from Natal, Brazil. "The emotion is so strong, the faith is so great."

Sobbing, she said she could feel John Paul's presence.

"I've seen Masses here on television, but I never imagined when I got here I'd feel him so close to me," she said.

Some of the pilgrims gazed up at the chimney on the slanted roof of the chapel, where white smoke will signal to the world that the church's 265th pontiff has been elected. The famous stove in the chapel, where the "princes" of the church were to convene later Monday, will billow black smoke to signal an inconclusive round of balloting.

The cardinals were to sequester themselves inside the chapel in the afternoon after a solemn procession from the Vatican's Apostolic Palace.

Many of the pilgrims said they would come to the square every day "to see what color the smoke comes out," according to Rigel Salazar, 42, of Ciudad Valles, Mexico.

"It's all because of John Paul. There hasn't been this sort of stirring before. He's really got the whole world thinking," said John Read, 65, a retired carpenter from Wales.

The crowds were smaller than those for John Paul's April 8 funeral, when hundreds of thousands of people packed the square and surrounding streets. But they grew as the day moved on, and many said the square would be packed by the time a cardinal cries from a Vatican balcony "Habemus papam" — "We have a pope" — however long it takes for that to happen.

The rainy skies that settled on Rome immediately after the funeral suddenly cleared Monday morning, giving way to a brilliant sunny day. Cloudy skies could make it difficult for some observers to determine the color of the smoke after balloting.

At the edge of the large column-lined square, people paused at a newsstand selling the Vatican newspaper L'Osservatore Romano, which on Monday featured a four-page spread with photos of each of the 115 voting cardinals — one of whom almost certainly will be the new pontiff. Although the conclave can elect any baptized Catholic male as pope, that has rarely been done.

Many of those in the square said they were praying for God to help the cardinals choose their new leader.

"Now what we are all hoping for is that the Lord illuminates the cardinals ... that the Lord through them makes the decision," said Rev. Luis Serrano, a 28-year-old priest from Isla Margarita, Venezuela, who is studying theology in Rome. "It is a very strong burden, choosing the pope who will guide the church."

He said he did not envy the cardinals charged with choosing the pontiff.

"They must feel fear and anxiety," Serrano said. "They are humans like anyone else. I wouldn't want to put myself in their shoes."

People from all continents mixed together on the square, all fixed on the giant screens showing the Mass.

"What impresses me is the universality of the church. There are Chinese, Japanese, Africans — we're surrounded by people from all places," said Javier Sancho, 40, a lawyer from Mendoza, Argentina. "It's beautiful that everyone is represented."