Lake Undozero Lake Undozero Lake Undozero () is a freshwater lake, located in the west of Plesetsky District of Arkhangelsk Oblast in Russia. It is one of the biggest lakes in Arkhangelsk Oblast and the second biggest one in Plesetsky District. The area of the lake is , and the area of its basin is . Lake Undozero is the source of the Undosha River, which belongs to the river basin the Onega River and thus to the White Sea basin. The lake has a sophisticated shape and contains a number of islands. The source of the Undosha is in the south-western
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