A road may be, for our purposes, most readily defined as the most convenient means of communication between two towns; and this logically implies that the towns existed before the roads were made; and in a fuller investigation of any particular roads, it will be necessary to start by investigating why men collect their dwellings at certain definite spots.  In the beginning, assemblies of men were made chiefly or altogether for defensive purposes, and the earliest towns were those which, from their natural position, like Athens or Jerusalem, could be most easily defended.  Then, again, religious motives often had their influence in early times, and towns would grow round temples or cloisters.  But soon considerations of easy accessibility rule in the choice of settlements, and for that purpose towns on rivers, especially at fords of rivers, as Westminster, or in well-protected harbours like Naples, or in the centre of a district, as Nuremberg or Vienna, would form the most convenient places of meeting for exchange of goods.  Both on a river, or on the sea-shore, the best means of communication would be by ships or boats; but once such towns had been established, it would be necessary to connect them with one another by land routes, and these would be determined chiefly by the lie of the land.  Where mountains interfered, a large detour would have to be made—­as, for example, round the Pyrenees; if rivers intervened, fords would have to be sought for, and a new town probably built at the most convenient place of passage.  When once a recognised way had been found between any two places, the conservative instincts of man would keep it in existence, even though a better route were afterwards found.

The influence of water communication is of paramount importance in determining the situation of towns in early times.  Towns in the corners of bays, like Archangel, Riga, Venice, Genoa, Naples, Tunis, Bassorah, Calcutta, would naturally be the centre-points of the trade of the bay.  On rivers a suitable spot would be where the tides ended, like London, or at conspicuous bends of a stream, or at junctures with affluents, as Coblentz or Khartoum.  One nearly always finds important towns at the two ends of a peninsula, like Hamburg and Lubeck, Venice and Genoa; though for naval purposes it is desirable to have a station at the head of the peninsula, to command both arms of the sea, as at Cherbourg, Sevastopol, or Gibraltar.  Roads would then easily be formed across the base of the peninsula, and to its extreme point.

At first the inhabitants of any single town would regard those of all others as their enemies, but after a time they would find it convenient to exchange some of their superfluities for those of their neighbours, and in this way trade would begin.  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