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
Onega River of the Onega is notable for the rapids, spread everywhere between Kargopol and Gorodok, and also located downstream from Porog (the name "Porog" means "a rapid"). The Onega basin area has an important historical and cultural significance. Kargopol is one of the oldest cities in Russian North (the traditional foundation date in the 12th century, first mentioned in the 14th century), and it still contains a big number of architectural and historical monuments. Oshevensk on the left bank of the Onega is the location of the former Alexandro-Oshevensky Monastery. Another historically important monastery in the Onega basin is the Kozheozersky