from Wikipedia Cotonou:
Cotonou is the economic capital of Benin, as well as its largest city. Its official population count was 761,137 inhabitants in 2006; however, some estimates indicate its population may be as high as 1.2 million. The population in 1960 was only 70,000. The urban area continues to expand, notably towards the west. The city lies in the southeast of the country, between the Atlantic Ocean and Nokoué Lake, located at 6°22' North, 2°26' East (6.36667, 2.4333).
In addition to being Benin's largest city, it houses many of its government and diplomatic services; thus, it is Benin's de facto capital, even though the official capital is Porto-Novo. The city is best known as a major port, thanks to the Autonomous Port of Cotonou; it is also home to an airport and a railway that links to Parakou. Other features of Cotonou include Cotonou Friendship Stadium, Cotonou Cathedral, Cotonou Central Mosque and the 20-hectare Dantokpa Market, which includes a fetish market and has a commercial turnover of over a billion CFA Francs a day. The National University of Benin is located in Cotonou. Another familiar feature of the city is the motorcycle-taxis known as Zémidjans.