Markets would become neutral ground, in which mutual animosities would be, for a time, laid aside for the common advantage; and it would often happen that localities on the border line of two states would be chosen as places for the exchange of goods, ultimately giving rise to the existence of a fresh town.

As commercial intercourse increased, the very inaccessibility of fortress towns on the heights would cause them to be neglected for settlements in the valleys or by the river sides, and, as a rule, roads pick out valleys or level ground for their natural course.

For military purposes, however, it would sometimes be necessary to depart from the valley routes, and, as we shall see, the Roman roads paid no regard to these requirements.
The earliest communication between nations, as we have seen, was that of the Phoenicians by sea.

They founded factories, or neutral grounds for trade, at appropriate spots all along the Mediterranean coasts, and the Greeks soon followed their example in the AEgean and Black Seas.

But at an early date, as we know from the Bible, caravan routes were established between Egypt, Syria, and Mesopotamia, and later on these were extended into Farther Asia.