The cathedral of Otranto in southern Italy is decorated with the skulls of 800 Christian townsfolk beheaded by Ottoman soldiers in 1480.
A week tomorrow, on Sunday May 12, they will become the skulls of saints, as Pope Francis canonises all of them. In doing so, he will instantly break the record for the pope who has created the most saints.
Benedict XVI announced the planned canonisations just minutes before dropping the bombshell of his own resignation. You could view it as a parting gift to his successor. Or a booby trap.
The 800 men of Otranto – whose names are lost, except for that of Antonio Primaldo, an old tailor – were rounded up and killed because they refused to convert to Islam. In 2007, Pope Benedict recognised them as martyrs "killed out of hatred for the faith".
That is no exaggeration. Earlier, the Archbishop of Otranto had been cut to pieces with a scimitar. Some accounts of the martyrdoms will raise a sceptical eyebrow: Primaldo reportedly remained standing after he was decapitated, a Pythonesque miracle that stretches credulity.
But the murders really happened, and their significance is immense. The Turks had been sent by Mohammed II, who captured the "second Rome" of Constantinople and planned to do the same to the first.
His fleet landed in Otranto, Italy’s easternmost city, and laid siege. The citizens held out for two weeks, allowing the King of Naples to muster his forces. Rome did not fall.
"All of this took place because of the indifference of the political leaders of Europe to the Ottoman menace," wrote the conservative Italian senator Alfredo Mantovano in an article about the martyrdoms in 2007.
"In Otranto, no one displayed rainbow pacifist flags, nor invoked international resolutions… Today Europe is under attack, not by an institutionally organised Muslim phalanx but by a patchwork of non-governmental organisations of fundamentalist Muslims."
Pope Francis desires warm relations with Islam – so, as I say, I wonder how pleased he was to discover this event in his diary. Already the interfaith lobby is squirming, always a fun sight.
But, equally, the Church can’t allow the ceremony to be hijacked by rabble-rousers. There are, however, good secular reasons for welcoming this canonisation.
Our history is distorted by a nagging emphasis on Christian atrocities during the Crusades combined with airbrushing of Muslim Andalusia, whose massacre of Jews in 1066 and exodus of Christians in 1126 are rarely mentioned.
Otranto reminds us that Islam had its equivalent of crusaders – mighty forces who nearly captured Rome and Vienna. The Muslim Brotherhood is still committed to a restored Caliphate; this week its supporters prophesied the return of a Muslim paradise to Andalusia.
These are pipe dreams, it goes without saying. But they matter because they inspire freelance Islamists whose fascination with southern Europe has nothing to do with welfare payments. They think of it as theirs because they know bits of history that we’ve forgotten.
Our amnesia comes in handy in dialogue with Muslims: we grovel a few apologies for the Crusades, sing the praises of the Alhambra, and that’s it. But what does this self-laceration achieve?
Arguably it’s counterproductive, because it shows Muslims that we’re ashamed of our heroes as well as our villains. Which is why the mass canonisation of 800 anonymous men is so welcome: it ensures that, even though the West has forgotten their names, it won’t be allowed to forget their deaths.