 There are "büyükşehir belediyesi" (or greater municipalities) for large cities like İstanbul or İzmir and consist of an extra administrative layer run by an elected head mayor, who oversees a number of municipalities and mayors.The districts and their populations (as of December 31, 2019) are listed below, by region and by province (with capital district in bold text).In 16 provinces with greater municipality the total population of the province is not equal to the summation of all district populations.