The Pontic Scythians practised trade extensively, and beginning in the 7th and 6th centuries BC, they had been importing luxuries such as personal ornaments, gold and silver vases, carved semi-precious and gem stones, wine, oil, and offensive and defensive weapons made in the workshops of Pontic Olbia or in mainland Greece, as well as pottery made by the Greeks of the Aegean islands; during the Classical Scythian period of the 5th century BC, the Scythians were importing Corinthian and Athenian pottery; and by the Mid-Scythian period of the 4th to 3rd centuries BC the market for Pontic Olbia was limited to a small part of western Scythia, while the rest of the kingdom's importations came from the Bosporan kingdom, especially from Panticapaeum, from where came most of Scythia's imported pottery, as well as richly decorated fine vases, rhyta, and decorative toreutic plaques for . An important trade route existed in Scythia during the Early Scythian period which started in Pontic Olbia and followed the course of the Inhul river and crossed the Dnipro, after which it turned east until the country of the Gelonians and, after crossing the Don and the Volga, passed through the Ural Mountains and continued into Asia. Gold was traded from eastern Eurasia until Pontic Olbia through this route, and the Scythian trade went to the distant regions on its course to carry out commerce. The conquest of the north Pontic region by the Scythians and their imposition of a "" created the conditions of safety for traders which enabled the establishment of this route. As a consequence of these flourishing trade relations, which were themselves possibly only thanks to the protection and cooperation of the Scythian kings, the Greek colonies on the northern shores of the Black Sea rapidly grew during the 6th century BC, and the Scythian upper classes were also able to significantly enrich themselves. The relations between the Scythians and the Greek cities became more hostile during the 5th century BC, with the former destroying the latter's and rural settlements and therefore their grain-producing hinterlands, with the result being that the Scythians instituted an economic policy under their control whereby the sedentary peoples of the forest steppe to their north became the primary producers of grain, which was then transported through the Southern Buh and Dnipro rivers to the Greek cities to their south such as Tyras, Niconium and Pontic Olbia, from