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.