 Other evidence of Roman presence was covered over the centuries by a thick layer of soil carried over the centuries by the Potok brook.During the Goth rule of Dalmatia in the 6th century, Byzantine emperor Justinian I built a series of defenses along the coast, including the one on the top of Gradina, in an attempt to reclaim the lands lost to invading tribes and to ensure safe passage of trade.Throughout centuries the Neretva channel was a very important merchant sea route.