The ancient Silk Roads were the sea and land economic corridors which connected Asia to Europe and Africa. Through these economic corridors the silk and the spices of Asia could reach Europe and Africa. According to George Friedman, some spices, like pepper, could sell as high as gold. The two most important points of the silk roads were Cairo (Egypt), as far as the sea lanes were concerned, and Constantinople (Istanbul), as far as the land routes were concerned. See map 1 from wikipedia.
For centuries there was a lot of competition between the Christians and the Muslims about the control of the Silk Roads. Whoever controlled these routes could impose taxes on the merchandise and earn huge amounts of wealth. Most of the time the Muslims were controlling the southern part of the Mediterranean Sea (Africa), and the Christians were controlling the northern part of the Mediterranean Sea (Europe). When the Muslims beat the Greeks in 1453, and took control of Constantinople (Istanbul), they dominated the sea and land lanes of the Silk Roads. See map 2.
What is very interesting is that today the situation is very similar, except that the important merchandizes are not spices, silk and wool, but oil and natural gas. Today Erdogan in Turkey, who is already in control of Constantinople (Istanbul), is trying to establish a friendly islamist government in Egypt i.e. Mohamed Morsi of the Muslim Brotherhood, and at the same time he attacks Israel and Syria, which are the only alternative routes to Europe. Trade and merchandize can change but geography always remains the same.