Globe & Mail.  We were supposed to be leaving the fortress by now, heading back to Benghazi in the four-wheel-drive minibus with a Tuareg's head stenciled on the front door. Below waited our tour guide and our government minder. But this was our first sunny afternoon after five days of weather much more like Scotland than North Africa -- hailstorms, rain, bone-chilling winds -- and a half-dozen of us lingered on the warm ancient roof of Qasr Libya, drinking in the hills, the wildflowers, the huge clear Mediterranean sky.

Then, as we got ready to climb down, Natalie Kampen spotted something.

We knew we were standing on a Byzantine fort, the stronghold of a wealthy bishop 1,500 years ago, but frankly we had no idea what might lie beneath us. The few English-language guidebooks we had were sketchy on the details.

So Kampen stretched her 5-foot, 3-inch frame along the cracked mortar of the roof, straining for a look beneath the eaves. Far below, barely visible, she could discern what looked like figures on a decorated surface.

''You see what's down there?" she said. ''I think it's a mosaic!"

This was the kind of moment Kampen had been hoping for. A professor of art history at Columbia University, she had spent years traveling the edges of the Roman empire: Tunisia, Bulgaria, France, Hungary, Egypt. But not Libya. Libya has Roman ruins punching through the sands like ragged teeth, but for Americans it was long illegal and often dangerous ground.

A guard in a turban approached. Silently, he produced a key to the building and we stepped inside.

An unlighted roof arched in vaults over our heads. The room spread out before us into dusky nooks and apses. This building was no fort: It was a Byzantine church, small and elegant, its mosaic floor patterned with stags, trees, curling vines, a cross. We wandered through, documenting it with our cameras, mulling over the symbols beneath our feet. We climbed back into the bus alive with the sense of discovery.

In Europe, I thought, this little church attached to the fort would be a tourist attraction. It would have its own postcards and ticket booth. Here, it didn't even have its own name.

''I'd waited 23 years to go," said Kampen, who once struggled for months trying, unsuccessfully, to obtain a decent photograph of a famous set of Roman carvings in a Libyan museum.

My wife is in the cult, too. She studies ancient Roman art, and when Kampen began planning her trip last fall -- a dozen or so specialists keen to see this part of Roman Africa firsthand -- she signed on for both of us.

This is how we found ourselves spending half of March in Libya, fingering souvenir Moammar Khadafy T-shirts, with trash fires burning outside our hotel room and store owners trying sweetly to start international friendships with three words of English.

Libyans on the street, upon learning we were American, would break into smiles and shake our hands just for visiting. At a bakery in one small town, the owner handed us three perfect pieces of baklava and would not let us pay.

It was in Tripoli, the morning after we arrived, that we got our first taste of Roman Africa. The city's chief tourist attraction is its museum, housed in a stout 500-year-old castle keeping watch over the harbor and the Mediterranean Sea. For our roving band of experts, its collection of Roman art was a revelation. The emperor Claudius, carved in marble, slumped humanly in his chair. Kampen stepped into one room and was surrounded by the very sculpted panels that she had once tried so hard to find in photographs.

Whole walls were covered with mosaics, one after another, like a lurid slide show of the Romans' fantasy lives: gladiator battles, villas with sweeping white colonnades, lascivious frolicking pygmies.

It wasn't difficult to discern the tastes and ambitions of the rich provincials who were trying with all their might, nearly 2,000 years ago, to outshine Rome itself.

So what was ancient Libya, exactly? The North African coast was first dotted by Phoenecian trading ports and a handful of Greek cities in the east. Then the Romans, bent on expansion and hungry for resources, overran the place. Soon they had knit it into a full-fledged province with model towns, water projects, and the complicated military and government structures typical of the empire. It has never been so organized since.

The Romans trapped wild animals in Libya and sent them by the shipload to Rome to be killed in gladiatorial games. They grew olives and exported the oil; at its peak, Africa was producing more olive oil than Italy. They loaded grain by the ton into the holds of their wooden ships. The profits were plowed back into the immense port cities along the coast, with amphitheaters, arches, and lavishly appointed villas.

Much of the booty in Tripoli's museum was found in Leptis Magna, an ancient city about 90 minutes' drive west of Tripoli and the birthplace of the Roman emperor Septimius Severus. Time has treated Leptis Magna gently. Unlike Rome, looted and overbuilt by centuries of popes and dukes, Leptis was largely ignored as the sand swept over its houses and streets.

When we got to Leptis Magna on our third day in Libya, our little group walked almost gleefully through its ruins. We poked through a fish market, moved from room to room in a towering public bath complex, scrambled up the seats of an ancient theater, and looked down on its columned stage. The vast amphitheater, carved from the coastal cliffs, dropped away below our feet in a dizzying ellipse. The north border of town was simply a long sandy beach, the edge of ancient Leptis being pounded slowly into sand by the turquoise Mediterranean.

Today, as Libya reenters the international community, its sites are being excavated more gently by Italians, Frenchmen, even some Poles. The British never really left, and even publish an archeological journal dedicated only to findings in Libya. Still, it is a struggle to find updated information about much of the country, and our squad of historians found themselves sharing wrinkled maps and arguing with local ''experts" about what, exactly, we were looking at.

This was especially true at Cyrene, a sprawling ancient city in the east settled by the Greeks and taken over by Rome. It required a nail-biting flight on Buraq Air, Libya's domestic airline, and a whole new wardrobe; the high cliffs of eastern Libya are one of the coldest and wettest parts of Africa, especially in March.

At Cyrene we found none of the orderly pomp of Leptis Magna. The Greeks built their city not around a port, but around a holy spring in the cliff that still flows from its dark tunnel in the mountain. This gave the city a magical feeling, a tumble of temples, cave baths, theaters, and houses erupting from the slopes like a mossy dream. Far below, on the coast, stood its port of Apollonia and a scattering of cliffside Byzantine churches.

Centuries of later building by Romans made Cyrene hard to get a grip on, and the local guides didn't always help; one lengthy argument ensued between a local archeologist, who insisted we were looking at a Roman emperor in one carved battle scene, and our art historians, who pointed out that the composition bore no resemblance to an imperial portrait.

Eventually, even the great Roman Empire lost its hold on Africa; cities like Cyrene and Leptis Magna were left abandoned, unprotected. The remaining residents lingered under the protection of Byzantine dukes and bishops, building small churches and fortresses like Qasr Libya, the strange little church-fort where we stood blissfully in the sun the day after we left Cyrene. By the 7th century, the Arabs would sweep away the last vestiges of Rome.

Today, those vestiges are a big reason tourists are returning, slowly, to Libya. They also pose a challenge for the country as it reopens to the world. We were delighted to scramble over ancient marble blocks without fences or guards to keep us off, but it's hard to imagine that as tourism picks up, Libya's patrimony could -- or should -- remain so unprotected.

At Sabratha, another of its great Roman cities, we were told that the museum was closed because it had been looted, and all the guards thrown in jail.

I recently called Kampen, who looked back on our adventure as a singular experience, but worried about what would come next. Two hundred years ago, the British and French ''saved" Libya's ruins by sailing off with boatloads of marble columns, and it would be a shame if this impressive slice of ancient Rome were reopened only to vanish again.

''All through the colonial period, it was easy pickings for whoever did have the power," Kampen said. ''Globalization is always kind of teetering on the edge of the new colonialism. When you look at a situation like Libya's, when they are about to develop tourism . . . are they going to be able to afford to protect stuff? They may have the best will in the world, and simply not have the money."