of goods, particularly slaves to Byzantium. During the Kievan era, trade and transport depended largely on networks of rivers and portages. By this period, trade networks had expanded to cater to more than just local demand. This is evidenced by a survey of glassware found in over 30 sites ranging from Suzdal, Drutsk and Belozeroo, which found that a substantial majority was manufactured in Kiev. Kiev was the main depot and transit point for trade between itself, Byzantium and the Black Sea region. Even though this trade network had already been existent, the volume of which had expanded rapidly in the 11th century. Kiev was also dominant in internal trade between the Rus towns; it held a monopoly on glassware products (glass vessels, glazed pottery and window glass) up until the early- to mid-12th century until which it lost its monopoly to the other Rus towns. Inlaid enamel production techniques was borrowed from Byzantine. Byzantine amphorae, wine and olive oil have been found along the middle Dnieper, suggesting trade between Kiev, along trade towns to Byzantium. The peoples of Rus' experienced a period of great economic expansion, opening trade routes with the Vikings to the north and west and with the Byzantine Greeks to the south and west; traders also began to travel south and east, eventually making contact with Persia and the peoples of Central Asia. In winter, the ruler of Kiev went out on rounds, visiting Dregovichs, Krivichs, Drevlians, Severians, and other subordinated tribes. Some paid tribute in money, some in furs or other commodities, and some in slaves. This system was called poliudie. Society The lands of Kievan Rus' were mostly made up of forests and steppes (see East European forest steppe and Central European mixed forests), while its main rivers all originated in the Valdai Hills: the Dnieper (, , ), and primarily populated by Slavic and Finnic tribes. All tribes were hunter-gatherers to a certain degree, but the Slavs were primarily agriculturalists, growing cereal grains and crops, as well as raising livestock. Before the emergence of the Kievan state, these tribes had their own leaders and gods, and interaction between tribes was occasionally marked either by trading goods or fighting battles. The most valuable commodities traded were captive slaves and fur pelts (usually in exchange for silver coins or oriental finery), and common trade partners were Volga Bolghar, Khazar Itil and Byzantine Chersonesus. By the