The medieval roads, even those of Roman origin, declined greatly,
because the toll it before serving to finance road maintenance
was used by feudal lords to their advantage as a source of
income. So the sea and the rivers themselves were very used to
trade, although the inland waterways subject to stay dry in summer
and ice in winter and floods. Before the discovery of America,
contact with the East was the main source of goods.
(SANTOS METROPOLITAN UNIVERSITY, COURSE OF HISTORY)