Estonia, officially the Republic of Estonia, is a country in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Russia. The territory of Estonia consists of the mainland, the larger islands of Saaremaa and Hiiumaa, and over 2,300 other islands and islets on the east coast of the Baltic Sea. Its capital city of Tallinn, along with the city of Tartu, are the country's two largest urban areas. The Estonian language, of the Finnic family, is the official language and the first language of the majority of nearly 1.4 million people. Estonia is one of the least populous member states of the European Union. Present-day Estonia has been inhabited since at least 9,000 BC. The medieval indigenous population of Estonia was one of the last pagan civilisations in Europe to adopt Christianity following the Northern Crusades in the 13th century. After centuries of foreign rule by the Teutonic Order, Denmark, Poland, Sweden, and the Russian Empire, a distinct Estonian national identity gained new momentum with the Age of Awakening in the mid-19th century. This culminated in the 1918 Estonian Declaration of Independence. Democratic throughout most of the interwar period, Estonia declared neutrality at the outbreak of World War II, but the country was repeatedly invaded and occupied, and ultimately annexed into the USSR. Throughout the de facto Soviet occupation, from World War II until 1991, Estonia's de jure state continuity was preserved by diplomatic representatives and the government-in-exile.