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 Oblast and the non-freezing harbour of Murmansk, lost its significance as the main trading harbour of the Russian Empire. However, in the early 20th century Arkhangelsk was an important starting point for Russian Arctic expeditions. For instance, in the 1830s Pyotr Pakhtusov sailed twice from Arkhangelsk to investigate and map Novaya Zemlya. In 1932 the "Icebreaker Sibiryakov" under the command of Vladimir Voronin, sailing from Arkhangelsk, crossed the Northern Sea Route in a single navigation. In 1918 and 1919, Arkhangelsk Governorate became one of the most active battlegrounds of the Civil War in Russia. On August 2, 1918, Arkhangelsk was occupied