From the Wikipedia page 
Nyamagana District is one of the seven districts of the Mwanza Region of Tanzania. It is bordered to the north by Ilemela District, to the east by Magu District, to the south by Misungwi District and to the west by the Mwanza Bay of Lake Victoria. Part of the region's capital, the town of Mwanza, is within Nyamagana District. The district commission's office is scheduled to be re-located to the Mkolani area of Mwanza town, but currently it is still in the old city hall in the centre of town.