The visit - the first time a pope has appeared before the Italian parliament - underscored the warmth that the country feels for the Polish-born John Paul, the first non-Italian pontiff in 455 years.
It also showed that Italy and the Roman Catholic Church have healed the wounds that a century ago prompted popes to call themselves "prisoners" of the Vatican rather than accept Italy's government as legitimate.
The pope referred to the once-strained relations but said the bonds were now strong. He said Italy's very identity "would be most difficult to understand without reference to Christianity, its lifeblood."
Lawmakers interrupted the speech about 20 times with applause and gave the pope a standing ovation, with some cheering "Viva il papa!" at the end of his speech. However, the visit was not without opposition. A few deputies said they wouldn't attend to underscore that Italy remains a secular country, and a dozen or so gay activists protested at a nearby piazza.
The speech had an unexpected outcome: A fugitive Mafia boss turned himself in after being inspired by the pope's comments on family values, said his lawyer, Roberto Tricoli. In September, Benedetto Marciante was convicted in absentia and sentenced to 30 years in prison for homicide and Mafia association, Tricoli said.
The pope, 82, covered most of the general topics he has addressed in his 24-year pontificate, including respect for the dignity of man, democracy, peace and justice. He decried the ongoing Israeli-Palestinian conflict and international terrorism "which has taken on a new and fearful dimension, involving in a completely distorted way the great religions. Christian countries, he said, should work for peace and not allow themselves "to be imprisoned by a 'logic' of conflict incapable of offering real solutions."
But his emphasis was on Italy - and particularly what he called "the crisis of the birth rate." While Italy is largely Roman Catholic, the church teaching that couples should be open to having children is not enthusiastically followed: Italy has one of the lowest birth rates in the world - 9.3 births per 1,000 inhabitants - and one of the oldest populations. Italian women on average have 1.23 children, a figure under the European Union average of about 1.48 and well under the American average of about 2.1.
The United Nations has warned that Italy's economic future is at risk because the shrinking work force won't be able to support its aging population without an influx of migrant workers.
The pope called the situation "another grave threat that bears upon the future of this country, one which is already conditioning its life and its capacity for development." "Above all, it encourages - indeed I would dare to say, forces - citizens to make a broad and responsible commitment to favor a clear-cut reversal of this tendency," he said.
Politicians, he said, should adopt initiatives that "can make the task of having children and bringing them up less burdensome both socially and economically." And parents should instill in their children strong moral values, while schools should develop in a "healthy climate of freedom."
The pope urged Italian authorities to grant clemency to prisoners, saying a reduction in their sentences "would be clear evidence of a sensitivity" that would encourage their rehabilitation. And he repeated his call for European leaders, who are drafting a new European Union constitution, to recognize the role Christianity has played on the continent.
The pope appeared in strong form, speaking clearly through the 45-minute speech and walking on his own, with a cane, to his car. The car was parked in a square outfitted with big-screen TVs that broadcast his speech live.
Anita Marchesi, a first-year university student from the Italian island of Sardinia, was among the throngs of people watching the speech, which she called historic and important for the country. "The pope is right in asking for more children," she said. "We're well aware of it in Sardinia, where the older generations all come from large families and most of us are one or two."
The speech represented the latest step in improving relations between Italy and the church, which ruled a vast swath of the Italian peninsula until the mid-19th century. When the new Italian army seized the territory when Italy was unified in 1861, the pope was only left with Rome and some coastal areas, which were finally taken in 1870.
At the time, the government guaranteed the pope independence within what is now the Vatican and offered to compensate the church for the lost lands. But Pope Pius IX refused to recognize the government and called himself a "prisoner" of the Vatican. The so-called "Roman Question" was resolved in 1929, when the Vatican and Italy signed a treaty that recognized both as sovereign entities.