The "Dead Cities" of northern Syria, actually suburbs of Antioch, were deserted in the 7th-10th centuries after continual natural disasters and warfare. Now the remains of over 100 small towns are giving insight into life in the Byzantine Empire.
From the article by Paul Sieveking in ForteanTimes:
"East of Antioch, in northern Syria, are the limestone uplands – roughly 90 miles (145km) north to south – where the so-called “Dead Cities” are to be found. “Dead Cities” is actually a bit of a misnomer: there are over 100 major sites and a total of 780 settlements, but the largest is little more than a country town. The remains of an astonishing 1,200 churches have been counted, the largest collection of religious ruins in the world. Population pressures made exploitation of these uplands economic, supplying olive oil and wine to the Empire. The pinnacle of prosperity came in the fourth to the sixth centuries AD, following Rome’s loss of its North African provinces, hitherto a major agricultural source, particularly in olive oil. Oil wealth had a different connotation to that of today. Antioch was the only city in the ancient world with public street lighting – fuelled by olive oil."