Koidu Town (also known commonly as Koidu, or Sefadu) is the fourth largest city in Sierra Leone (after Freetown, Bo and Kenema) and the capital, largest city, and economic center of the diamond-rich Kono District in the Eastern Province. The city is a major business, commercial and diamond trade center. Koidu Town is the second largest city in the Eastern Province (after Kenema), and lies approximately 275 miles east of Freetown. The city's municipality is officially known as Koidu–New Sembehun. The municipality of Koidu–New Sembehun had a population of 82,899 in the 2004 census (a 2006 estimate being 111,800).