The Bank is a mid-level building that boosts a city's Gold output. The Great Merchant Giovanni de' Medici can be used to instantly build a Market and a Bank, and the Bank gains 2 Great Work slots which can be filled by any Great Work including Relics.
Although there had been money-lenders and treasuries before (money, after all, greases the wheels of civilization), banking begins in early Renaissance Italy, in the rich cities of the north such as Genoa, Venice, Florence, Siena and Lucca. During the 14th Century, already wealthy, avaricious families – the Bardi, de Medici, Peruzzi, Cerchi, Gondi and others – not only dominated the commercial banking in their home city-states but established branches across Europe. The oldest bank still in operation is the Monte dei Paschi in Siena, operating continuously since 1472 AD. Banking spread across the Holy Roman Empire and the northern European nations by 1600, and the Europeans took the practice with them when they set out to colonize the world. Although the details have changed dramatically with technology, the basics of banking profits remain the same: checking and savings fees, loans and credit cards, currency exchanges, fund management, and so forth.