The city contains the ruins of what, according to UNESCO, "was one of the most important cultural centers of the ancient world" — an important Silk Road hub where East met West more 2,000 years ago. A World Heritage Site, Palmyra is heralded by experts as having some of the finest Roman-era ruins in existence.
"It makes Rome blush," says Stephennie Mulder, an archaeologist and professor of Middle Eastern Studies at the University of Texas at Austin. "When you approach the site, it rises out of the desert like some sort of a mirage out of a fairy tale."
The ancient city, which flourished in the 1st and 2nd centuries, has numerous historic structures. Among them: a 3,600-foot long colonnade, an agora (or marketplace), an amphitheater, an urban quarter, a series of tombs, a hilltop castle and the Temple of Bel (also spelled Ba'al), an important, cross-cultural religious site pagan site.
In addition to executing 17 people in the area, according to some accounts — including, quite possibly, children — the fear now is that ISIS, which has wreaked destruction on other important ruins sites, will now get around to tumbling a crown jewel.
Palmyra is a monument to antiquity. Here is what made it — and what still makes it — important:
1. It is among the world's oldest settlements
"We as Americans can't appreciate the history that is there," says James Gelvin, a professor of Middle Eastern history at UCLA, who last visited Palmyra in the 1990s. "When we talk about the places that vie to the be oldest inhabited place on Earth, Palmyra is the sort of location you think about."
Though the city is often associated with the Roman Empire, under which it attained prominence, its history extends well beyond that. In fact, the city is mentioned in tablets that date as far back as the 19th century BCE. It grew in importance as a caravan stop in the third century BCE, an important desert pit-stop between the Mediterranean and the Euphrates River in Iraq.
"When you approach Palmyra, it's really about the journey through the desert and this green oasis emerges and you find yourself in this amazing place," says Andrew Smith, author of "Roman Palmyra: Identity, Community, and State Formation," as well as a professor of Classics at George Washington University. "In the first century, [the Roman author and naturalist] Pliny the Elder described it as an island in a sea of sand."
2. It is one of the most exquisite intact ancient ruins sites in the world
"Visually and architecturally, there are very few sites in the Roman world that have this much architecture in tact," says Mulder, who lived in Syria for 12 years. "Palmyra has been out there in the middle of the desert and hasn't been subjected to intense urbanization. It puts Rome to shame ... That's what makes it so amazing. You can essentially walk into a 2,000-year-old city."
"The Romans really built on a scale in the Eastern provinces that was unprecedented anywhere in the Empire," she adds. "In archeology, there is only one other place that takes my breath away in the approach, and that's probably [the ancient city of] Baalbek, in Lebanon."
Gelvin concurs that it a place of "tremendous power."
"How do you radiate authority when you don't have the same communications that we have today?" he asks. "You do that by building these massive structures. So when you arrive, you feel overwhelmed. It is just extraordinary."
The ruins have survived as long as they have because they have generally been respected.
"Muslims have long lived quite comfortably with sites like this for over 1,400 years," says Mulder. "There's nothing inherent to Islam about the way these sites are viewed. All of this is a very modern interpretation of Islam — embracing the notion that any kind of intercessor between human beings and god is a form of idolatry. ISIS has destroyed Islamic shrines, too. It's a heritage terror or a form of genocide, erasing the past in order to create a purified ideal."
3. Palmyra was an important hub, where East met West
"Palmyra was a nexus of interaction," says Smith. "You might see one brother wearing a Roman toga and another wearing Persian trousers. That's what's interesting about it."
"It looks Greco-Roman, but if you look closely you see Persian and Semitic styles, as well as influences from India and China," explains Mulder. "Some of the funerary sculptures display facial features from Indian sculpture."
In fact, one of its most remarkable structures — the Temple of Bel — is emblematic of the ways in which different cultures worked together. During its apex, 2,000 years ago, previously nomadic ethnicities settled in the city, and all of these contributed to the construction of monuments.
"They each contributed what they could to these buildings," Smith says. "And we know this by the inscriptions. All over the place, you see inscribed something along the lines of 'here's the wealthy patron who contributed this column.' The city is covered in these inscriptions. And what they show is different people coming together to build."
"Syria has always been a multicultural, multifaith, multiethnic place," adds Mulder, "and people have found a way to live together. Over its history, it's had Christians, Muslims, Jews and so many others that have co-existed over so many millennia. That's the history that Isis would like to eliminate with its history of purified Islam."
4. It was an important pagan site
Palmyra's peak was before the dawn of Islam (in the 7th century) and before Christianity had become a regional phenomenon (when the Roman emperor Constantine the Great was baptized in the early 4th century).
"The whole city is pagan," says Smith. "This was a pagan community."
Says Mulder: You have a temple to the god Baal who was a kind of Semitic storm god," says Mulder. "He was part of a triad of deities that was worshiped there. He was roughly the equivalent of Jupiter in the Roman canon, though this was part of their own canon of deities."
This is what makes the site so vulnerable to ISIS.
"It is the perfect symbol of the idolatry they claim to be trying to eradicate," adds Mulder. "I'm waiting to see if they blow up that temple."
5. The ruins are a symbol of Syria
As the ongoing civil war between Bashar al-Assad's government and a number of opposition forces are in the process of tearing the country apart, Palmyra stands as an important symbol of national identity.
"Syria is a brand-new country," says UCLA's Gelvin. "There was no Syria until after World War I. And then it was under French mandate. It had been carved up by the French. It only got independence in 1946. And when that happened, Syria had to establish a national narrative. Palmyra is part of that narrative."
Part of that has to do with the rule of Zenobia, a 3rd century Palmyrene queen who not only resisted Roman rule but also conquered a number of Rome's eastern provinces, including Egypt.
"So these extraordinary ruins," Gelvin says, " along with the story of Zenobia, become this symbol of resistance to imperialism."
Losing Palmyra will mean losing a piece of Syrian identity at a time when that identity is relentlessly fractured.
"What we also lose is a link to the past," he adds. "We lose something awe-inspiring. We lose something with real meaning."
Find me on Twitter @cmonstah.