In case you didn't notice, it's the Dark Ages again and Rome may soon be under siege by snarling, bloodthirsty invaders waging Holy War.

At least that's according to Abu Bakr al-Baghdadi, the leader of militant group Islamic State of Iraq and Syria (ISIS), in an audio recording marking the start of Ramadan last week. After swiftly seizing vast territories in Iraq and Syria, it appears he has now set his sights on the capital of Christendom as part of his stated intention to expand the self-proclaimed caliphate.

"In this virtuous month or in any other month, there is no deed better than jihad in the path of Allah," said al-Baghdadi in the recording posted online. "So to arms, to arms, soldiers of Islam, fight, fight. Rush O Muslims to your state. It is your state. Syria is not for Syrians and Iraq is not for Iraqis. The land is for the Muslims, all Muslims. This is my advice to you. If you hold to it you will conquer Rome and own the world, if Allah wills."

Despite its medieval tone and apparent absurdity, the threat against the place that once launched the Crusades must be taken seriously, the Italian government has warned, both for its real and symbolic implications. And, while a conventional military strike on any Western city is unthinkable, analysts caution that the Sunni extremists are capable and perhaps willing to use terrorism beyond their Middle East strongholds.

Meanwhile in Rome, it's business as usual. At least on the surface.

'Those who bark like dogs don't scare us.'

On Sunday morning, thousands of the faithful and the curious flocked to St Peter's Square to see Pope Francis pray his weekly Angelus, the first since ISIS made its threat.

A group of a dozen white-clad nuns scoffed at the notion of fear."The blood of martyrs is the seed of the Church," says Sister Henid Haddad, 48, from Lebanon. "We derive our strength in the resurrection of Christ. Those who bark like dogs don't scare us."

Meanwhile, person after person, backpack after backpack, purse after purse flooded before the pontiff without the kind of security checks one might expect after a threat from a group with a proven track record of living up to its word. ISIS also has a blatant disregard for civilian life and was deemed too much of a publicity hazard even for its former al Qaeda allies, who disowned them.

At Rome's central train station, scurrying passengers barely noticed a reporter and his notebook, much less whether there's been a security escalation.

"What security? This is Italy. You know how it is. People get on and off trains without the kinds of checks you find at the airport. Anything could happen," Marco Natalini, a 34-year-old engineer who licked a gelato as he waited for his train, told VICE News. "This is a big city. If terrorists wanted to do something, there's little the police could do besides cleaning up the mess".

Barak Mendelsohn, a senior fellow at the Foreign Policy Research Institute and an associate professor of political science at Haverford College, says al-Baghdadi's rhetoric should not be dismissed wholesale.

"Of course Rome is the symbol of Christianity," he told VICE News, recalling that even Abu Musab al-Zarqawi, an al Qaeda leader at the height of the Iraq war, made references to sacking Rome before he was killed in an airstrike in 2006. "Al-Baghdadi is cloaking himself in the religious authority of the caliphate, he could be serious. One threat may be the large number of his fighters who are from Europe. Presumably they'll eventually go home, and they'll be seasoned."

In May, four people were killed at the Jewish Museum in Brussels, allegedly by a gunman who spent over a year fighting with ISIS. The suspect, Mehdi Nemmouche, is thought to be the first Syrian militant to commit attacks upon returning to Europe.

'If someone is looking for attention, all he has to do is grow a beard and threaten people.'

Italy has been all but immune to violent acts of Islamic terrorism since 9/11. Mendelsohn speculated that this might be to do with the country's important geographical position between the Christian and Muslim worlds.

"It likely serves jihadi interests to keep a low profile in Italy given the country's important logistical location between North Africa and the rest of Europe. Jihadists are better off preserving Italy as a strategic corridor." But Mendelsohn confessed: "I am surprised by the lack of violence so far."

Diplomats and prominent Muslim leaders in Rome have downplayed the ISIS threat on the Eternal City.

"If someone is looking for attention, all he has to do is grow a beard and threaten people," Saywan Sabir Mustafa Barzani, Iraq's ambassador to Rome, told VICE News. "More than 99 percent of the victims of remorseless terrorist violence are in the Middle East, and threats on Rome and non-Muslims are driven by propaganda."

The head of the Italian Islamic Cultural Center, hosted inside the Grand Mosque of Rome, says that acknowledging the ISIS threat risks legitimizing it."Common sense tells us that this much-hyped conquest of Rome is nothing more than a deception tactic," Abdellah Redouane told VICE News. "It has nothing to do with the true faith."

'These people are totally ignorant of history.'

Yet some local Muslims feel the ISIS proclamation deserves immediate rebuke from the Islamic community, whether it is credible or not. "We as Muslims in Rome should say something. An attack on the city would naturally be an attack on us as well," said Mustafa Cenap Aydin, head of the Istituto Tevere, a center for interreligious studies.

"This is the cradle of civilization for the whole world. We all use the Gregorian calendar. We all use the Roman legal system. Any attack against Rome should not be considered only in the context of the Crusades, but also as an affront to civilization, democracy, and basic rights and freedoms."

From his office overlooking the Tiber River, Aydin playfully recalls how here, in the year 846, Arab raiders daringly sailed upstream, plundered St. Peter's, and sacked the city, before ultimately being repelled by Pope Leo IV. "I think ISIS is even less sophisticated than those invaders," said Aydin. "These people are totally ignorant of history."

He admitted, however, that ISIS is nefarious and savvy when it comes to wielding religion as a sharp weapon, in a battle that is just as much psychological as it is territorial.

"Compared to Europe and the West, society in Iraq and Syria is still very religious. You can mobilize people through religious discourse. And there's a huge level of ignorance in those areas, unfortunately, but it's a fact you have to recognize," Aydin said, comparing the mindset of today's ISIS fighter to that of a Crusader in the Middle Ages."I think ISIS is more or less using the same ideology."