Arkhangelsk Oblast the south-west of the Oblast drains into the Kema River which belongs to the basin of the Caspian Sea. The area in the Onega River basin containing the biggest lakes in the oblast, such as Lake Lacha, Lake Kenozero, Lake Undozero, and Lake Kozhozero. The tundra of the Nenets Autonomous Okrug also contains a number of bigger lakes. The river basin of the Pinega is characteristic of the karst, with a number of caves in the region. The White Sea coast within the Oblast is split into the Onega Bay (where the Onega is the major tributary), the Dvina Bay
Arkhangelsk evidence of a stronger case of Russian colonization than previously thought. In the 12th century, the Novgorodians established the Archangel Michael Monastery (named after Michael the Archangel) in the estuary of the Northern Dvina River. The main trade center of the area at that time was Kholmogory, located southeast of Arkhangelsk, up the Dvina River, about downstream from where the Pinega River flows into the Dvina. Written sources indicate that Kholmogory existed early in the 12th century, but there is no archeological material to illuminate the early history of the town. It is not known whether the origin of this