The Silk Road or Silk Route was an ancient network of trade routes that for centuries were central to cultural interaction through regions of the Asian continent connecting the East and West from China to the Mediterranean Sea. While the term is of modern coinage, the Silk Road derives its name from the lucrative trade in Chinese silk carried out along its length, beginning during the Han dynasty (207 BCE – 220 CE). The Han dynasty expanded Central Asian sections of the trade routes around 114 BCE, largely through missions and explorations of the Chinese imperial envoy, Zhang Qian. The Chinese took great interest in the safety of their trade products and extended the Great Wall of China to ensure the protection of the trade route. Trade on the Silk Road played a significant role in the development of the civilizations of China, the Indian subcontinent, Persia, Europe, the Horn of Africa and Arabia, opening long-distance political and economic relations between the civilizations. Though silk was certainly the major trade item exported from China, many other goods were traded, and religions, syncretic philosophies, and various technologies, as well as diseases, also spread along the Silk Routes. In addition to economic trade, the Silk Road was a route for cultural trade among the civilizations along its network.
The Silk Road consisted of several routes. As it extended westwards from the ancient commercial centres of China, the overland, intercontinental Silk Road divided into northern and southern routes bypassing the Taklimakan Desert and Lop Nur.
The northern route started at Chang'an , an ancient capital of China that was moved further east during the Later Han to Luoyang. The route was defined around the 1st century BCE when Han Wudi put an end to harassment by nomadic tribes. The northern route travelled northwest through the Chinese province of Gansu from Shaanxi Province and split into three further routes, two of them following the mountain ranges to the north and south of the Taklamakan Desert to rejoin at Kashgar, and the other going north of the Tian Shan mountains through Turpan, Talgar, and Almaty (in what is now southeast Kazakhstan). The routes split again west of Kashgar, with a southern branch heading down the Alai Valley towards Termez (in modern Uzbekistan) and Balkh (Afghanistan), while the other travelled through Kokand in the Fergana Valley (in present-day eastern Uzbekistan) and then west across the Karakum Desert. Both routes joined the main southern route before reaching ancient Merv, Turkmenistan. Another branch of the northern route turned northwest past the Aral Sea and north of the Caspian Sea, then and on to the Black Sea. A route for caravans, the northern Silk Road brought to China many goods such as "dates, saffron powder and pistachio nuts from Persia; frankincense, aloes and myrrh from Somalia; sandalwood from India; glass bottles from Egypt, and other expensive and desirable goods from other parts of the world." In exchange, the caravans sent back bolts of silk brocade, lacquer-ware, and porcelain.
The southern route or Karakoram route was mainly a single route running from China through the Karakoram mountains, where it persists in modern times as the international paved road connecting Pakistan and China as the Karakoram Highway. It then set off westwards, but with southward spurs enabling the journey to be completed by sea from various points. Crossing the high mountains, it passed through northern Pakistan, over the Hindu Kush mountains, and into Afghanistan, rejoining the northern route near Merv, Turkmenistan. From Merv, it followed a nearly straight line west through mountainous northern Iran, Mesopotamia, and the northern tip of the Syrian Desert to the Levant, where Mediterranean trading ships plied regular routes to Italy, while land routes went either north through Anatolia or south to North Africa. Another branch road travelled from Herat through Susa to Charax Spasinu at the head of the Persian Gulf and across to Petra and on to Alexandria and other eastern Mediterranean ports from where ships carried the cargoes to Rome.