If the Vatican looked askance at this religious arriviste three kilometres from St. Peter's Basilica, it made no comment.
That sumptuous mosque, opened in 1995, cost $50 million to build, a cost borne by 23 Muslim donor nations, though the bulk of funding – $35 million – was contributed by Saudi Arabia.
A country which, by the way, allows no Christian churches on its soil, even with an ever-expanding influx of Christian migrant workers from such places as the Philippines and Indonesia.
An estimated 800,000 Catholics work in Saudi Arabia now. Indeed, celebrating non-Muslim holidays in the cradle of Islam is forbidden, as are crosses and the wearing of a crucifix.
The Vatican quietly made it known, earlier this year, that high-level discussions were underway with Saudi officials – this after King Abdullah made a first ever visit to St. Peter's last November – aimed at some kind of reciprocal arrangement that might, once diplomatic relations are fully secured, allow for the construction of churches in the kingdom.
The mosque in Rome, which welcomes tourists, is a place of education as well as prayer. And there certainly needs to be a lot more education, on both sides, to combat ignorance and mutual distrust.
Rome has, in fact, three mosques and three Islamic prayer centres. A fourth mosque, in an ethnically mixed neighbourhood, was halted mid-construction last summer. There had been outrage from Roman Catholics because the structure was a conversion of a building situated right next door to a Catholic church.
Municipal officials insist that was not the reason for kyboshing the project; rather, the Muslim constituency that had commissioned the mosque had failed to secure proper building permits. Which, yes, sounds quite lame.
Relative to other European capitals such as Amsterdam, Rome doesn't have a huge Muslim population. But, given the Vatican's history and the Christian crusades that spilled so much Muslim blood, it behooves the papal state – and the secular city surrounding it – to be as tolerant of other faiths as possible.
In truth, the Vatican is intensely envious of Islam, not only as the world's most rapidly growing religion, but also for the ferocity of its adherents and the way in which faith invests every aspect of their daily life.
For most who bow at least symbolically to Rome, Catholicism is a cafeteria-tray buffet, pick what you like off the menu, ignore the rest, and pull out all the stops only at Christmas and Easter. And maybe on your death bed, for last rites, the absolution of all sins.
Pope Benedict XVI was severely criticized last week for the very public and perhaps gratuitously showy conversion of a Muslim man – a journalist outspoken in his criticism of "radical" Islam – in what has been described as a "triumphalist'' episode, pointlessly provocative.
But there was a point.
Catholicism is as evangelical – if not capital-E Evangelical – as any other religion. Baptizing a convert from Islam was a celebratory moment for the pontiff, and there haven't been many lately. By contrast, converting from Islam is an act of apostasy in some Muslim countries, subject to a death sentence.
A friend of mine in Afghanistan was jailed last year after revealing to friends that he was considering converting to Christianity. It took great effort by Western intermediaries to spring him and he has sought asylum in Germany.
The secular world, which the Vatican fears as much as its Islamic counterpart, has learned how easily provoked some Muslim societies can be. This is piety run amok, not faith.
All religions are opiates. You should at least get to pick your poison.
Rosie DiManno usually appears Monday, Wednesday, Friday and Saturday.