Bosra stands on the black basalt plain of the Hauran, in the south of Syria, close to the Jordanian frontier, and the whole town seems to be made of the dark volcanic stone that is found in the fields. It was a Nabataean town, and then the Romans made it the capital of the province of Arabia in the early second century, building a grid of streets, baths, a triumphal arch and one of the best-preserved theatres in the Roman world. The theatre could seat some fifteen thousand people. In the Middle Ages it was wrapped in a fortress by the Ayyubids, whose walls and towers rise around the stage, so that you can walk through the vaults beneath the seats and the old defences at the same time.
Bosra stood on the pilgrim and trade routes to Mecca and Damascus, and later it was a place of pilgrimage itself. A monastery, according to tradition, was the home of the monk Bahira, who recognised the young Muhammad as a future prophet when his uncle's caravan stopped here. The town has some of the earliest mosques in Syria, including the Mosque of Omar, with columns reused from Roman buildings. Many of the houses are old, and families lived among the ruins for centuries, with wells, cisterns and small shops. It was listed by UNESCO in 1980.
The label places it on a ride that passes the desert castle region, and the names in the area are mixed up, but the real place is Bosra. Look for current advice from official sources, and be prepared for the answer to be that you cannot go.
When access is possible, the surrounding plain is open farmland, with wheat, olive groves and stone-walled fields, and the roads run straight through the black rock country. The Hauran villages are built of basalt, and the doorways and lintels are often carved. Busra ash-Sham is a small town close to the ruins, and larger towns lie further away, so fuel is an issue to plan. The heat in summer is fierce, with winds from the desert, and the best seasons are spring and autumn.