According in the administrative area of Nairobi , 3,138,295 inhabitants lived within 696 km2 .
With a population in 2011 , Nairobi is the second - largest city by population in the African Great Lakes region after Dar es Salaam , Tanzania .
According in the administrative area of city , 3,138,295 inhabitants lived within 696 km2 .
With a population in 2011 , Nairobi is the second - largest city by population in the African Great Lakes region after Dar es Salaam , Tanzania .