 The city was granted the "right of transit" and started to gain significant profit from the goods transported between the Black Sea and the Baltic.In the following centuries, the city's population grew rapidly and soon Lwów became a multi-ethnic and multi-religious city as well as an important centre of culture, science and trade.The city's fortifications were strengthened, with Lviv becoming one of the most important fortresses guarding the Commonwealth from the south-east.