Galata's history stretches back some 2000 years, and it has always been autonomous region (officially or unofficially). Indeed, the area used to be surrounded by protective walls. Galata has long been the center of two vastly different sectors: the banking and prostitution.
From Frommer's Review
The neighborhood of Galata, located on a steep hump of land north of the Golden Horn and historic peninsula, actually sits on the earliest foundations of the city, dating, as far as present-day archaeologists can tell, to Greek and Roman times. At one time, it was covered in gardens and vineyards; indeed the ancient Greeks called the district "Sykai," meaning "place of fig gardens," and later, the hilly expanse became known as "peran en Skai," or "fig gardens on the other shore." Or just plain Pera. There is also speculation that the name Galata comes from the Italian word for descent (calata), an appropriate description of the steep and staired streets that slope down the hill from Beyoglu to the Golden Horn. The district developed into its present form in the 13th century, when Eastern Roman Emperor Michael VIII Palaeologus granted the Genoese permission to settle here.
The district became a magnet for merchants from all over Europe: Italians, Germans, Armenians, Jews, and Austrians, all re-creating their own micro-universe. The Genoese remained neutral during the Ottoman siege, so when Mehmet the Conqueror took over the city, although he installed his own Ottoman administration and assumed control of all commercial affairs, the Sultan granted them, along with the other minority communities, substantial commercial privileges. The ensuing commercial prosperity of the district fed trade throughout the Mediterranean and acted as a magnet for foreigners and ethnic minorities who established the district as centers of business, shipping, and banking. Serving the center of the financial district was a row of stately financial institutions lining both sides of what is now alternately called Bankalar Sokagi (Bank St.) and Voyvoda Caddesi. Bankers wishing to settle near their places of business constructed dignified residences for themselves and their families, and serving the community was a full complement of schools, churches, and synagogues.
As Galata prospered, the population burst its boundaries to incorporate the neighborhoods northward (and eventually up to and along the Grand Rue de Pera or Istiklal Caddesi). A stroll up and down the steep cobbled streets will reveal schools, private residences, churches, synagogues, and Ottoman-era warehouses. (There are also the ruins of a mikva or Jewish bathhouse in dire need of restoration opposite the former private mansion of the Camondo banking family, now the Galata Residence.)