Answer:
The city of Constantinople, today Istanbul (the most important city in Turkey), was located on the Bosphorus Strait, which marks the border between Europe and Asia Minor, as well as was in the middle of the trade route between Europe and the Middle East.
Therefore, during Roman times, Constantinople was one of the most important cities of the Empire and the capital of the Eastern Roman Empire after its division. After the fall of this empire at the hands of the Ottomans, the Muslims began to control the area and to put limits to the commerce of the West with the East.
