The mobility of the people in the Roman empire was sometimes surprisingly high. Travelling around was quite common – young ambitious members of noble families didn’t hesitate to relocate in order to receive the best possible education, retired soldiers often stayed in the new provinces… But from time to time, the population of a whole city was moved at one. One would expect this being a result of some horrible war and enslavement of the population, but it was not always the case.
In fact, we know about one occasion when a city was abandoned and then rebuilt just a couple of miles from its original site. All this work was done for health-related reasons. The city was called Salpia (or Salapia) and it could be found in Apulia region of the southeast Italy (near the modern town called Trinitapoli). The city was truly ancient and derived its origin from the famed hero Diomedes who supposedly founded Salpia on his way back from the Trojan war. Alternatively, a much less know guy from Rhodes called Elpias was considered to be its founder.
Regardless of their identity, the founders didn’t do a good job when selecting the site. The city stood dangerously close to marches. Everyone, whoever founded a city, will tell you that such sites are to be avoided. While rivers are great as a source of water, or means for transportation, marches stink and tend to increase the likelihood of illnesses.
Year after year, the good people of Salpia suffered from illnesses. They loved their city but hated the sickness that was way too frequent there. After many years they finally decided to take action. You would expect them to move out of the city. They did. In fact, they moved their whole city. A public petition was organized and after the Roman authorities approved the plan, the whole city of Salpia was moved some four miles away – to a new and healthier site by the sea.
Vitruvius – The Ten Books on Architecture