White Sea small. The main island group is the Solovetsky Islands, located almost in the middle of the sea, near the entrance to Onega Bay. Kiy Island in Onega Bay is significant due to a historic monastery. Velikiy Island, located close to the shore, is the largest island in the Kandalaksha Gulf. The White Sea is a water-filled depression in the block of a continental shelf known as the Baltic Shield. Its bottom is very uneven and contains the Kandalaksha Hollow in the northwest and the Solovetsky Islands in the south. Also, the Onega Bay has many small underwater elevations. The opening
Arkhangelsk Oblast also navigable in the lower course. The Onega is not navigable except for the two relatively short stretches because of the rapids. However, except for the lower course of the Vychegda and some parts of the Northern Dvina, there is currently very little or no regular passenger navigation on these rivers. They are used for cargo traffic though. In 1765, a road was built between Saint-Petersburg and Arkhangelsk, mainly for postal service. The road still exists and passes Kargopol and Plesetsk, and it has been paved in 2011. One of the principal highways in Russia, M8, connects Moscow and Arkhangelsk,