Koidu Town (also known commonly as Koidu or, or Sefadu) is the capital, largest city, and economic center of the diamond-rich Kono District in the Eastern Province of Sierra Leone. Koidu Town is the fifth largest city in Sierra Leone by population (after Freetown, Bo, Kenema and Makeni) and the second largest city in the Eastern Province, after Kenema. The city is a major business, commercial and diamond trade center, and lies approximately 285 miles east of Freetown.