The biggest cement factory in sub-Saharan Africa has been opened in Nigeria by Africa's richest man, Aliko Dangote.
The Obajana plant in the central Kogi State is expected to produce about 10 million tonnes of cement a year.
It is one of the country's biggest investments outside the oil sector in recent years.
BBC Nigeria correspondent Will Ross says there is reason to be optimistic about Africa's economic prospects.
Nigeria's economy is expected to grow by about 6% this year.
However, analysts warn that the growth is not reaching all sectors of society and the gap between the rich and poor is growing ever wider.
Our correspondent says the ceremony was a glitzy affair, with plenty of personal wealth on display as Nigeria's elite came together to celebrate industrial success.
He adds that Chinese workers in bright orange overalls were among the guests - a Chinese firm installed the latest line at the plant.
President Goodluck Jonathan called the plant a "quantum leap" for Nigeria's cement sector.
The Dangote group has invested some $6.5bn (£4.2bn) in the sector in recent years.
There are also plans to expand the Obajana plant to make it the world's biggest.
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