Most old towns are lost. Look at the maps drawn by Strabo and Ptolomeo: not one in ten is still around. What happened to them all? How can a whole town disappear?
Map of Europe according to Strabo (time of Christ)
Remember that those old towns, sometimes called cities, were no more than villages by our standards. They were a little cuddling together of maybe fifty houses. Most didn’t have a wall around them, so there’s no big orderly pile of rocks to signal archaeologists. And the houses themselves were made of adobe, which after they were abandoned became just a heap of dirt.
It actually helps excavators locate them if an enemy had razed the town because then they find a nice, even, layer of ash as they uncover the mound.
But some of those long-gone cities meant a lot in ancient times and were the scenes of great battles and the hometowns of famous emperors and other famous people. Trajan was from Itálica, now a vast marble junkyard near Seville, and Hannibal’s wife was from Cástulo, a mound just south of Linares.
To look for old Iberian towns like Cástulo archaeologists refer to the maps by the Greeks mentioned above—Strabo and Ptolomeo.
Map of Hispania according to Ptolomeo (first century AD) from LÓPEZ-DAVALILLO LARREA, JULIO: Atlas Histórico de España y Portugal: desde el Paleolítico hasta el siglo XX, Ed. Síntesis, 1999.)
For Roman towns they use two good sources: the Antonine Itinerary and the Vicarello Cups.
The Antonine Itinerary was probably made at the beginning of the third century. It charts thirty-four main roads and all the cities and towns, with the distance between them in Roman miles (1481 meters). And even better, it records partial distances between mansio and mansio, that is, between points that represented a days’ march and which served as resting stops and places to change horses.
The other great source, the Vicarello Cups, are four silver cylinders engraved with all the stops on the trip between a shrine in northern Italy (the Aquae Apollinares) and the temple of Hercules in Cadiz, Spain. The cups are exvotos offered by Spaniards who made the pilgrimage about the end of the first century. Like the Antonine Itinerary, the cups list all the towns and cities on the way, plus the mansioni and the distances between them.
Already in prehistoric times, there were two main roads around the peninsula. At first the Romans used and improved those. The oldest and most travelled was precisely the route on the Vicarello Cups: the route through the Pyrenees and down the western and southern coasts all the way to Cadiz.
That they called the Via Herculea or later, the Via Augustea.
The other famous road was the Via de la Plata, which paralleled the modern Portuguese-Spanish border. It went from Mérida to the rich mineral mines in Galicia.
The road along the Portuguese coast and a northern route straight to the gold mines and Galicia were the other Mother Roads.
Here is a map of Hispania (Spain in Roman times). For a large version click here
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Great Names in History 
Madame Monet: That last idea of yours is good. And remember wars. Spain has had such a long and troubled history. It has been invaded many times, starting with the first Celts who no doubt destroyed a few native Iberian towns. Vanquishing armies often destroy an enemy town completely or order its inhabitants to go elsewhere. Hannibal wiped Althaea off the map–that was the chief city of the Olcades; the Romans levelled many rebel towns. There was a great economic crisis in the third century. Most cities shrank because trade broke down. City dwellers moved to some rich man’s villa for food and protection against invading barbarians and roving bands of brigands. When the Moors came many towns were abandoned and the populace fled to fortified cities. With different places to defend, the Moors established towns and fortresses in other parts of the country, bypassing old towns. After Christian kings had conquered one of the Moorish strongholds, they tried to populate it and drew Spaniards away from their hometowns with incentives (free land, no taxes, etc.). So many reasons. Actually, few were abandoned because of a lack of water. All the native Iberian towns look the same: a hill above a creek.
I am very interested in this subject. Please, could you clarify something for me? Why was it that these small towns were abandoned, in your opinion? Was it something like they ran out of water? Or was it simply that there became a lack of economic opportunities in that place? (The modern equivalent would be a major highway is built along a different route, and fewer people take the old route, lessing the income to a town.) What do you think?
Eileen
Dedicated Elementary Teacher Overseas (in the Middle East)
elementaryteacher.wordpress.com