Lapland is the largest and northernmost region of Finland. The 21 municipalities in the region cooperate in a Regional Council. Lapland borders the Finnish region of North Ostrobothnia in the south. It also borders the Gulf of Bothnia, Norrbotten County in Sweden, Finnmark County and Troms County in Norway, and Murmansk Oblast and the Republic of Karelia in Russia. The topography of Lapland varies from vast mires and forests in the south to fells in the north. The Arctic Circle crosses Lapland, so polar phenomena such as the midnight sun and polar night can be viewed in this region.