Andrew Lawler is a freelance journalist who covers archaeology and cultural heritage in the Middle East.

In March 2011, as she had done every Friday afternoon for years, Jenny Poche Marrache held court at her 16th-century compound in the heart of Aleppo’s sprawling ancient market. Wearing a fur-lined leather coat to ward off the spring chill, the tiny 72-year-old regaled visitors with stories of this city’s cosmopolitan past. When her great-grandfather — a Bohemian crystal merchant — arrived here two centuries ago, Aleppo had already been a hub of East-West trade for half a millennium. Carpets from Persia, silks from China and high-quality local textiles filled the warehouses and stalls. Even at the height of the Crusades, Venetian agents exchanged timber and iron for Indian spices in the city’s souks.

In the midst of Syria’s civil war, more is being lost than lives. Aleppo may be the world’s oldest continuously occupied city, dating to the era of the pyramids, and at the height of the Ottoman Empire, it was the world’s largest metropolis after Istanbul and Cairo. That antiquity, wealth and diversity left behind magnificent mosques with Mameluke minarets, Ottoman-style bathhouses, and neoclassical columns and balustrades overlooking traditional courtyards tiled with marble and splashed by fountains. But Aleppo’s legacy extends beyond historic buildings. The city welcomed people of many faiths and traditions, while its old rival Damascus, a holy city and a gateway to Mecca, was long out of bounds for Westerners. Muslims, Christians and Jews created Syria’s commercial hub and one of the most tolerant, long-lasting and prosperous communities in the Middle East. “What was sold in the souks of Cairo in a month was sold in Aleppo in a day,” Madame Poche said, quoting a Syrian adage.

As we sipped coffee the week that the civil war began, this refined, prosperous world was already long in decline. “The situation is deplorable,” Madame Poche said in French-accented English, looking with disdain at the crates of cheap Chinese shoes filling the courtyard. Neighborhood merchants complained that the local textile mills had shut down, forcing them to replenish their stock with inferior cloth from Dubai. Despite Aleppo’s status as a World Heritage Site, many old buildings were in serious disrepair. And the once-vibrant Jewish community had vanished.

Since my first visit to Aleppo two decades ago, a coalition of entrepreneurs, city planners and foreign experts began the formidable task of rescuing and restoring one of the cultural and architectural jewels of the Middle East. Last year I walked along the new promenade surrounding the moated and massive ancient citadel. I stayed at one of the bed-and-breakfasts that had sprung up amid the warrens of covered markets to cater to foreign tourists, and I visited a recently uncovered 4,500-year-old temple. At an art gallery, I chatted with a photographer who helped organize an edgy international arts festival — an event unthinkable in dour Damascus.

The growing recognition of Aleppo’s importance in Middle Eastern history and culture makes the burning of the old city all the more tragic. In recent online videos, flames crackle in the closely packed alleys of the covered bazaar, smoke billows from a medieval caravansary, and an armed fighter gestures at the collapsed dome of a 19th-century mosque. Reportedly, more than 500 shops in the 71 / 2 miles of streets within the region’s largest marketplace have been damaged. The minaret of a 14th-century school is now only a stump. The entrance of the medieval citadel is cratered, and the fortress’s huge wooden gates are gone. A car bomb last week blew out the windows of the Aleppo Museum, one of the world’s best collections of Near Eastern artifacts.

And the fighting continues.

Amid the terrible human suffering — many remaining residents have no running water or electricity, and they lack food amid the nightmare of guerrilla warfare — concern about the destruction of material property can appear gratuitous. But the ancient urban fabric of Aleppo is more than an exotic tourist destination. “The Aleppo souks . . . stand as testimony to Aleppo’s importance as a cultural crossroads since the second millennium B.C.,” says Irina Bokova, director general of UNESCO. She promised an investigation, though the conflict will make it hard to assess damage, much less protect what is left. “The situation is really catastrophic, as Aleppo is half destroyed,” Michel Amalqdissi, director of the Syrian government’s archaeology division, e-mailed me last week.

Nor is destruction limited to this commercial hub. Five of Syria’s six most important ancient sites reportedly have been damaged, and massive looting of the country’s ancient heritage may be underway. Archaeologists fear that the losses could dwarf those that occurred in Iraq after the U.S.-led invasion. Syria has arguably the richest and most diverse history of any nation on Earth. It is home to the ruin of what may be the world’s first city, a mound near the Iraqi border called Tell Brak, as well as the famous Roman-era desert city of Palmyra, the Crusader fortress Krak des Chevaliers and some of Islam’s greatest monuments. Thousands of smaller sites encompass more than 10,000 years of human history, from Neolithic villages to Hittite strongholds, Roman forts, early Christian monasteries and Umayyad palaces. Lacking protection, these sites are open to mass theft that will feed the West’s hungry antiquities market.

The day after our coffee, Madame Poche’s son took me to lunch at a fashionable restaurant in a restored Ottoman palace in today’s Christian quarter. At the next table, a half-dozen clergy of different Christian sects drank wine and chatted while Sunni businessmen in suits talked deals nearby. At the time, Egypt’s revolution was only a distant rumble, and those I spoke with dismissed the idea of a revolt in a mercantile city tolerant of minorities. Aleppo, they noted, took in thousands of Armenians fleeing Turkey a century ago and did the same with Iraqi Christians after 2003. We didn’t know about the arrest of several boys in the southern town of Daraa that week. Three days after my lunch, the first open demonstration against the Syrian regime took place. Since then, most of Madame Poche’s family, and thousands of other Christians, have fled to Lebanon, Turkey and the West. She, however, remains in her beloved city. “I’m worried about my old house,” she e-mailed me Monday.

Aleppo’s remarkable history of diversity and tolerance — a model for a region in turmoil — is itself perilously close to becoming history. That past is an important bridge to a prosperous future that requires a well-educated populace linked to the wider world. Amid the destruction of a great city, there is more to mourn than shattered stone.