Sites in Angola, South Africa and Eritrea have been added to the Unesco World Heritage list.
Mbanza Kongo city in Angola, the Khomani Cultural Landscape in South Africa and Asmara, the capital of Eritrea, were added to the list announced on Saturday.
The decision was made during the 41st session of the Unesco World Heritage Committee in Warsaw, Poland.
Mbanza Kongo is currently the capital of northwestern Zaire Province.
The Angolan province is located some 481km north of the capital Luanda, and shares borders with both the Democratic Republic of Congo and the Congo-Brazzaville.
Mbanza Kongo, the capital of the Kongo Kingdom, was founded before the arrival of the Portuguese in 1483.
It also served as an economic, social and cultural centre.
Eritrea, in the Horn of Africa, still holds many well-preserved modernist buildings from the time when it was ruled by Italy (1889-1941).
Unesco said Asmara was "an exceptional example of early modernist urbanism at the beginning of the 20th century and its application in an African context".
Eritrean authorities declared the city a national monument in 2001, and had been attempting for years to gain recognition for its architectural heritage.
More than 400 modernist buildings survive in Eritrea, having lived through a decades-long conflict with Ethiopia.
Famous among them is the Fiat Tiaglero building, a petrol station shaped as an aeroplane. Built in 1938, it now stands empty.