The network of routes commonly known as the "Silk Road" resulted from an expansion of commercial and cultural exchanges between China and the Tarim Basin. Ferdinand von Richthofen labeled numerous primary and secondary overland routes of commercial and cultural exchanges across Central Asia the "Silk Route" or "Silk Road" (Seidenstraáe) in the late nineteenth century. The routes around the Takla Makan desert in the Tarim Basin connected the Chinese capitals at Ch'ang-an (modern Xi'an) and Loyang with the western frontiers from the Han to Tang periods. The routes divided into northern, southern and central branches around the Tarim Basin at Dunhuang.
The northern route started from the Jade Gate outside of Dunhuang and proceeded to the oasis of Turfan, near the Buddhist cave complex at Bezeklik. From Turfan, this route followed the southern foothills of the Tien-shan mountains to Karashahr and Shorchuk (near modern Korla) before reaching Kucha, an oasis surrounded by Buddhist cave complexes such as Kyzil and Kumtura. The northern route continued through Aksu, a junction for routes over the Tien-shan, and Maralbashi, near the Buddhist caves of Tumshuk, to Kashgar, where the southern route reconnects.
The southern route began at the Yang-kuan gate outside of Dunhuang and continued to oases on the southern rim of the Takla Makan desert such as Miran, Charklik, Cherchen, Endere, and Niya. This route followed the northern base of the Kun-lun mountains to Khotan and Kashgar. An intermediate route from Dunhuang led to the military garrison at Lou-lan on Lop-nor Lake, where branches diverged to Miran on the southern route and Karashahr on the northern route. Travelers' itineraries around the Tarim Basin depended on their goals and destinations, the political and physical environment, and economic conditions.
In the broadest sense, the silk routes extended to the Mediterranean along the itinerary described in the Parthian Stations by Isidore of Charax in the first century CE (translated by Wilfred Schoff). Overland routes led from the Mediterranean through Syria to Mespotamia, ancient Iran, and Margiana (Merv) in western Central Asia. Routes from Margiana reached Bactria in the Oxus valley, or branched northwards to Sogdia and continued through the Ferghana valley and across the Alai range to Kashgar. Capillary routes through the Karakoram mountains directly linked the silk routes of eastern Central Asia with the major arteries of the Indian subcontinent. The "northern route" (Uttarapatha) extending from Bactria to northern India was connected to the "southern route" (Dakshinapatha) in the Deccan plateau and seaports on the western coast of India. ThePeriplus Maris Erythraei describes prosperous maritime trade between western and southern India, Arabia, Egypt, and the Roman Empire during the first century CE.
Many artifacts demonstrate long-distance trade connections and cultural transmission between China, Khotan on the southern silk route, and the northwestern frontiers of the Indian subcontinent. Fragments of finely woven tabby silk from China reflect long-distance trade or tribute relations with Khotan during the third or early fourth centuries CE. Coins of Indo-Scythian (Saka) and Kushan rulers (see essays on Sakas and Kushans) and an incomplete manuscript of a Gandhari version of the Dharmapada were found near Khotan. Other items imported to Khotan from the northwestern Indian subcontinent included small Gandharan stone sculptures and moulded terracotta figures. Long-distance trade in highly valued Buddhist items (such as manuscripts, small sculptures, miniature stupas, and possibly relics) prefigured later connections between Buddhist communities in Khotan and Gilgit. Khotan was not only a regional commercial and religious center of the southwestern Tarim Basin, but also functioned as a connecting point between China, India, western Central Asia, and Iran.
The Shan-shan kingdom, which flourished on the southern silk route between Niya and Lou-lan until the fourth century CE, benefited from long-distance trade between China and eastern Central Asia. In exchange for luxury items from these regions, Chinese silk was probably used in commercial transactions, since silk was preferred to copper coins as currency. The economic prosperity of agricultural oases and trading centers on the southern silk route enabled Buddhist communities to establish stupas and monasteries. As Marilyn Rhie observes in Early Buddhist Art of China & Central Asia (vol. 1, p. 429), Buddhist sculptures from Miran and Khotan display many similarities with the artistic traditions of Gandhara, Swat, and Kashmir in the northwestern Indian subcontinent. Mural paintings at Miran reflect ties with both the art of western Central Asia and northwest India (Rhie, p. 385). Administrative documents found at Niya, Endere, and Lou-lan written in the Gandhari language and Kharosthi script demonstrate linguistic and cultural ties between the southern silk route oases and the northwestern Indian subcontinent in the third to fourth centuries CE .
Intermediate routes through Karashahr and northern routes through Turfan probably eclipsed the southern route by the fifth century CE (according to Rhie, p. 392). Many of the most important archaeological sites on the northern silk route are clustered around Kucha and the Turfan oasis. Mural paintings in cave monasteries, stupa architecture, artifacts, and other remains from approximately the third to seventh centuries at sites around Kucha show closer stylistic affinities with the northwestern Indian subcontinent, western Central Asia and Iran than with China. Sites located further east along the northern silk route belonging to relatively later dates in the seventh to tenth centuries typically reveal more Chinese and Turkish elements. Mural paintings from the cave monastery of Kyzil demonstrate continuities between the art of the western part of the northern silk routes and the artistic traditions of Swat, Gandhara and Sassanian Iran in the middle of the first millennium CE. Monks and merchants traveling on the northern and southern silk routes were responsible for maintaining commercial, religious, and cultural contacts between India, Central Asia, and China.
Material remains from sites along the silk routes reflect close relations between long-distance trade and patterns of cultural and religious transmission. Demand for Chinese silk and luxury commodities which were high in value but low in volume stimulated commerce. Valuable items such as lapis lazuli, rubies, and other precious stones from the mountains of Afghanistan, Pakistan, and Kashmir probably led travelers to venture into these difficult regions. Some of these products became popular items for Buddhist donations, as attested in Buddhist literary references to the "seven jewels" (saptaratna) and reliquary deposits (see Xinru Liu, Acient India and Ancient China, pp. 92-102). Long-distance trade in luxury commodities, which were linked with the transmission of Buddhism [see essay on Buddhism and Trade], led to increased cultural interaction between South Asia, Central Asia, and China.