The administrative centre of the district is Zainsk. Area – 1842,4 square km. The city of Zainsk is situated at the confluence of two rivers – Stepnoy Zai and Lesnoy Zai, 287 km to the east of Kazan, and has a railway station. Zainsk was founded between 1652 and 1656 as a fortress. Since 1978 Zainsk is a city.