On a wintry afternoon, the basalt theatre in the Greco-Roman city of Gadara in northern Jordan can appear forbiddingly bleak. Its builders, however, knew how to break the drabness. “Like this,” says architect Boris Bogdanovic as he picks up two fragments of white marble from the ground and juxtaposes them on the edge of the stage. The marble cornice that adorned the edges of the 3,000-capacity venue has all broken off or been stolen. It could have come from present day Greece, or Italy, Mr Bogdanovic says. The theatre resembles a larger one in Bosra, another basalt city 95 kilometres to the east, in present day Syria. The city, which was Nabatean, fell to Roman suzerainty in the second century. While Bosra, regarded as one the greatest sites of antiquity in the Levant, is practically off limits to most tourists because of the upheaval in Syria, a visit to Gadara could compensate for what they cannot see across the border. Both cities were situated on trading routes – to the Mediterranean in the case of Gadara and to the Red Sea in regard to Bosra, which was the larger commercial centre. Bosra even featured in the life of the Prophet Mohammed, who accompanied caravans from inner Arabia to the city when he was young. Gadara had an estimated population of 30,000 people, less than half that of Bosra. The two cities received water through advanced aqueducts. They flourished under the emperors Trojan and Hadrian, renowned builders in Imperial Rome. The ruins of Gadara and Bosra are fairly typical of Roman cities: theatre, baths, colonnaded streets, cisterns and a large public fountain, as well as shops and houses. But they are unusual in that they are largely black or dark grey. Gadara's infrastructure remains are also impressive: one cistern in the city is 10 metres deep by 11 metres wide. A gravity-based water system that supplied the city stretched 170 kilometres into the Syrian interior. It was largely comprised of tunnels, parts of which survive. They were among the longest built in the ancient world. From almost anywhere in Gadara there is a view of the Sea of Galilee in present day Israel; the Golan Heights, which Israel has occupied since 1967; and the valley of the Yarmouk, a main tributary of the Jordan river. Bosra became capital of the Roman province of Arabia Petraea (Stony Arabia), although it is situated on the edge of the Great Syrian Desert. Gadara was capital of the Decapolis, a league of 10 Greek cities in the Levant, of which Bosra was not a member. The Decapolis allied with Rome and was bound by security and commercial interests. Menippus, a satirist and a disciple of the Cynic philosopher Diogenes, was born in Gadara. A few kilometres away is the site of the 636 AD Battle of Yarmouk , one of the most significant, and by some accounts, one of the bloodiest, military encounters before the invention of modern weapons. The defeat of the Byzantines by the Rashidyn dynasty marked a significant expansion of Islam and the end of Byzantine rule over Syria. Mr Bogdanovic says the Gadara theatre bears uncanny resemblance to the one in Bosra, and both could have been built by the architect Apollodorus of Damascus. But he cautions that this is only a hypothesis that needs more research. He supervises restoration work at the theatre and in a 19th-century village on the edge of Gadara, on behalf of Turquoise Mountain, a charity founded by Prince Charles. A New Zealander born in the Balkans, Mr Bogdanovic says Gadara's natural location enhanced its defences. He also describes it as "a very healthy place", citing the ancient Romans' affinity for holidaying in Gadara and enjoying the city's sights, baths, wine, theatre and a diverse plant cover. "Gadara was a more poetic place," he says.