Question: Where can you find the majority of gold in the southernmost country of the continent where the river serving as drainage for the southwest plain of the Congo is found?

full_context: Document 1: Kimberley, Northern Cape: Kimberley is the capital and largest city of the Northern Cape Province of South Africa. It is located approximately 110 km east of the confluence of the Vaal and Orange Rivers. The city has considerable historical significance due to its diamond mining past and the siege during the Second Boer War. British businessmen Cecil Rhodes and Barney Barnato made their fortunes in Kimberley, and the roots of the De Beers company can also be traced to the early days of the mining town.
Document 2: Republic of the Congo: Congo is located in the central-western part of sub-Saharan Africa, along the Equator, lying between latitudes 4°N and 5°S, and longitudes 11° and 19°E. To the south and east of it is the Democratic Republic of Congo. It is also bounded by Gabon to the west, Cameroon and the Central African Republic to the north, and Cabinda (Angola) to the southwest. It has a short coast on the Atlantic Ocean.
Document 3: Geography of Angola: Angola is located on the western Atlantic Coast of Central Africa between Namibia and the Republic of the Congo. It also is bordered by the Democratic Republic of the Congo and Zambia to the east. The country consists of a sparsely watered and somewhat sterile coastal plain extending inland for a distance varying from . Slightly inland and parallel to the coast is a belt of hills and mountains and behind those a large plateau. The total land size is . It has an Exclusive Economic Zone of .
Document 4: Republic of the Congo: The Republic of the Congo's sparse population is concentrated in the southwestern portion of the country, leaving the vast areas of tropical jungle in the north virtually uninhabited. Thus, Congo is one of the most urbanized countries in Africa, with 70% of its total population living in a few urban areas, namely in Brazzaville, Pointe-Noire or one of the small cities or villages lining the 534-kilometre (332 mi) railway which connects the two cities. In rural areas, industrial and commercial activity has declined rapidly in recent years, leaving rural economies dependent on the government for support and subsistence.
Document 5: Congo River: Railways now bypass the three major falls, and much of the trade of Central Africa passes along the river, including copper, palm oil (as kernels), sugar, coffee, and cotton. The river is also potentially valuable for hydroelectric power, and the Inga Dams below Pool Malebo are first to exploit the Congo river.
Document 6: Mayombe: Mayombe (or Mayumbe) is a geographic area on the western coast of Africa occupied by low mountains extending from the mouth of the Congo River in the south to the Kouilou-Niari River to the north. The area includes parts of the Democratic Republic of the Congo, Angola (Cabinda Province), the Republic of the Congo and Gabon.
Document 7: Mitumba Mountains: The Mitumba Mountain range stretches along the Western Rift Valley in Eastern Congo (DRC), west of lake Tanganyika. The two main peaks, Mount Kahuzi (3,308 m) and Mount Biéga (2,790 m) are extinct volcanoes.
Document 8: Republic of the Congo: The Republic of the Congo (French: République du Congo), also known as Congo, Congo Republic, West Congo[citation needed], or Congo-Brazzaville, is a country located in Central Africa. It is bordered by five countries: Gabon to the west; Cameroon to the northwest; the Central African Republic to the northeast; the Democratic Republic of the Congo to the east and south; and the Angolan exclave of Cabinda to the southwest.
Document 9: Geography of Cambodia: Cambodia's low mountain ranges - representing the walls of the bowl - remain as the result of only rather recent substantial infrastructural development and economic exploitation - in particular in remote areas - formidably forested. The country is fringed to the north by the Dangrek Mountains plateau, bordering Thailand and Laos, to the north - east by the Annamite Range, in the south - west by the Cardamom Mountains and in the South by the Elephant Mountains. Highlands to the north - east and to the east merge into the Central Highlands and the Mekong Delta lowlands of Vietnam.
Document 10: Yumbi: Yumbi is a town and territory in Plateaux District of Bandundu Province in the Democratic Republic of the Congo. It lies on the eastern bank of the Congo River between Bolobo and Lukolela.
Document 11: South African rand: The South African rand (sign: R; code: ZAR) is the currency of South Africa. The rand is subdivided into 100 cents (sign: ``c ''). The ISO 4217 code is ZAR, from Dutch Zuid - Afrikaanse Rand (South African rand). The rand is legal tender in the Common Monetary Area between South Africa, Swaziland, Lesotho, and Namibia, although the latter three countries do have their own currencies.
Document 12: Gold Fields: Gold Fields Limited is one of the world’s largest gold mining firms. Headquartered in Johannesburg, South Africa, the company is listed on both the Johannesburg Stock Exchange (JSE) and the New York Stock Exchange (NYSE). The firm was formed in 1998 with the amalgamation of the gold assets of Gold Fields of South Africa Limited and Gencor Limited. As of the third quarter of 2014, Gold Field was the world's seventh-largest producer of gold.
Document 13: South African rand: The rand takes its name from the Witwatersrand ("white waters' ridge" in English), the ridge upon which Johannesburg is built and where most of South Africa's gold deposits were found.
Document 14: Republic of the Congo: The southwest of the country is a coastal plain for which the primary drainage is the Kouilou-Niari River; the interior of the country consists of a central plateau between two basins to the south and north. Forests are under increasing exploitation pressure.
Document 15: Rand Stadium: The Rand Stadium is a stadium in Rosettenville, a suburb of Johannesburg, South Africa. It was set to be utilized as a training field for teams participating in the 2010 FIFA World Cup after being completely rebuilt and reopened in August 2008. Despite the relatively small capacity, it is regarded as one of the best playing surfaces in the country.
ground_truth: Witwatersrand
sub_queries: Which river serves as drainage for the southwest plain of the Congo? Answer: Kouilou-Niari River
Kouilou-Niari River >> continent Answer: Africa
Where can you find the majority of gold in the southernmost country in Africa ? Answer: Witwatersrand