A Bank increases tax revenue produced in its city by 50%, in addition to any Marketplace benefit. You must have a Marketplace to build a Bank.
A highly developed banking system is one of the cornerstones of an advanced civilization. Banks lend money to individuals or groups, providing capital for industrial and real estate development. Banks also contribute to the economic growth of a city or region by stimulating the development of production facilities. Individual citizens can also benefit by investing their own surplus money in the bank and earning interest on it.