The following question refers to the information contained in this passage.
The city of Dubrovnik has a rich and complicated history. For centuries it served as a halfway point between the Ottoman Empire and the Christian nations of Europe. After the Ottoman Empire invaded and conquered much of the Balkans, trade between the Empire and Christian Europe was largely forbidden, except through the independent city-state of Dubrovnik (at the time called Ragusa). Considering the massive amount of trade that poured through Dubrovnik on the way from the East to the Italian city-states and the nations of Northern Europe, it is no surprise that the city grew immensely wealthy and developed an autonomous character.
The main idea of this passage centers around __________________.