Sierra Leone (Listeni/sɪˈɛərə lɪˈoʊni, -lɪˈoʊn/), officially the Republic of Sierra Leone, is a country in West Africa that is bordered by Guinea to the northeast, Liberia to the southeast, and the Atlantic Ocean to the southwest. Sierra Leone is a constitutional republic with a directly elected president and a unicameral legislature. The country has a tropical climate, with a diverse environment ranging from savannah to rainforests. Sierra Leone has a total area of 71,740 km2 (27,699 sq mi) and with an estimated population of 6 million (2011 United Nations estimate). Freetown is the capital, largest city, and its economic and political centre. Bo is the second largest city and second major economic center. Sierra Leone is divided into four administrative regions: the Northern Province, Eastern Province, Southern Province and the Western Area; which are subdivided into fourteen districts. Each district has its own directly elected local government known as district council, headed by a council chairman, in whom local executive authority is vested. Since Independence to present, Sierra Leone's politics has been dominated by two major political parties: the Sierra Leone People's Party (SLPP) and the All People's Congress (APC). Currently all 124 elected seats in the Sierra Leone House of Parliament are held by members of either the APC or the SLPP. About sixteen ethnic groups inhabit Sierra Leone, each with its own language and custom. The two largest and most influential are the Temne and the Mende. The Temne are predominantly found in the north of the country, while the Mende are predominant in the south-east. Sierra Leone is a predominantly Muslim country, though with an influential Christian minority. Sierra Leone is regarded as one of the most religiously tolerant countries in the world. Muslims and Christians collaborate and interact with each other peacefully in the country. Religious violence is very rare in Sierra Leone. Although English is the language of instruction in schools and the official language in government administration, the Krio language (derived from English and several indigenous African languages) is the primary language of communication among Sierra Leone's different ethnic groups, and is spoken by 90% of the country's population. The Krio Language serves to unite the different ethnic groups, especially in their trade and daily interaction with each other. Sierra Leone has relied on mining, especially diamonds, for its economic base. It is also among the largest producers of titanium and bauxite, a major producer of gold, and has one of the world's largest deposits of rutile. Sierra Leone is home to the third-largest natural harbour in the world. Despite exploitation of this natural wealth, 70% of its people live in poverty. In 1462, the Portuguese explorer Pedro de Sintra visited this area, naming it Serra de Leôa, meaning "Lioness Mountains", for the landscape around Freetown. Posts in Sierra Leone were developed as centres of the Atlantic slave trade, and hundreds of thousands of Africans were transported from the interior to the Americas through trading posts in Sierra Leone. Britain planted a colony in the peninsular area of Sierra Leone in 1787 as a place to relocate black poor from London, but it was overcome by native hostility. In 1792 Freetown was founded as a colony for freed slaves who had fought on the British side during the American Revolutionary War. About 1,200 Black Loyalists were resettled from Nova Scotia on 11 March 1792; they were mostly African Americans from the former colonies, now the United States. In 1808, Freetown became a British Crown colony. Their descendants are known today as the Sierra Leone Creole people. In 1896, Britain annexed the interior of the country as a British protectorate, changing its relations with the paramount chiefs. The united country achieved independence in 1961. Government corruption and mismanagement of the country's natural resources finally lead to the Sierra Leone Civil War (1991 to 2002), which over more than a decade devastated the country. It left more than 50,000 people dead, much of the country's infrastructure destroyed, and over two million people displaced as refugees in neighbouring countries.