A glance at a map shows vast stretches of the inner parts of Asia dominated by mountains and desert. The mountains include some of the highest in the world. Around the year 400, a Chinese monk named Faxian traveled to India through the Karakorum Range and noted the dangers of the route:

The snow rests on them both winter and summer. There are also among them venomous dragons, which, when provoked, spit forth poisonous winds, and cause showers of show and storms of sand and gravel. Not one in ten thousand of those who encounter these dangers escapes with his life.

In fact though, were it not for those snow-covered mountains, there would be no life in Inner Asia, for they store in their snow and glaciers the moisture which feeds the rivers that make agriculture in the lowlands possible. The Franciscan, John of Plano Carpini's observations from the 13th century are relevant here:

In some parts the country is extremely mountainous, in others it is flat, but practically the whole of it is composed of very sandy gravel...[and] is completely bare of trees. Not one hundredth part of the land is fertile, nor can it bear fruit unless it be irrigated by running water....

He is describing the Gobi--that vast gravel desert of northern Central Asia, which is one of the several deserts occupying huge swatches of the continent. The name of the most intimidating of all these deserts, the Taklamakan, is revealing—the place where he who goes in does not come out. More than the mountains, the desert could test the traveler's will to live: Xuanzang's biographer tells us how he nearly perished on its northern fringes: "Time seems to stop... For four or five days the pilgrim and his horse struggle westward. Not a drop of water anywhere. His mouth, lips, and throat are parched by the burning heat. The evening of the fifth day the horse and rider fall down exhausted...." Without the mountains, no water; without water, no life; no fertile oases, no terraced fields of Central China.

Moreover, the cooling of the air as it rises over the mountains produces precipitation which waters the lush pastures inhabited by nomads and their flocks. When Marco Polo traveled through the Hindu Kush mountains of northeast Afghanistan and beyond them the Pamirs, he noted:

This is said to be the highest place in the world. And when he is in this high place, he finds a plain between two mountains, with a lake from which flows a very fine river. Here is the best pasturage in the world; for a lean beast grows fat here in ten days. Wild game of every sort abounds. There are great quantities of wild sheep of huge size. Their horns grow to as much as six palms in length and are never less than three or four....

Now the important thing here is not the sheep we now know as the Marco Polo sheep, Ovis poli, but the fact that important areas of Inner Eurasia are ideally suited to pastoral nomadism. The nurturing landscape for the emergence of some of the great nomadic empires was often that of Mongolia and Manchuria, where the rolling hills provided ample pasturage and there was water from the melting snow. Sedentary peoples relying on agriculture would not live there, but the necessities of life (for the most part) could be obtained from the animals which constituted the nomads' wealth.

The geography of the Silk Roads then is a complex interaction between the physical and climate zones of mountain, steppe or grasslands, and river valleys and oases which often are bounded by uninhabitable desert. Thus populations could be dispersed (in the grasslands) or concentrated in the oases and river valleys. Despite carefully developed adaptation to an environment that was at one productive and harsh, life for pre-modern man in Eurasia was not easy. Populations were especially vulnerable to disease and unexpected natural calamities in a way that tends (there are exceptions, of course) not to be so true today.

Movement from one habitable location to another in pre-modern times would be possible only where water was to be found along the way and the barriers of physical geography presented no obstacles to travel on foot or on the backs of animals. Movement could be "vertical" or "horizontal." The former would be the common pattern for many nomadic herders, whose seasonal cycle took them up into the mountain pastures in the summer and back to the lower elevations in winter. For interaction with the "outside world," horizontal movement over often quite long distances, even if cyclical, was essential. From the modern perspective, where we are accustomed to the idea that one can travel almost anywhere at any time thanks to technology, the geographical limitations on such travel in pre-modern times may seem formidable indeed. It is hard for us to imagine people walking or riding hundreds or thousands of kilometers. Indeed, our early Silk Road travelers convey some sense of the challenges. Regarding the near vertical slopes of the Indus River gorge, Faxian writes:

The way was difficult and rugged, running along a bank exceedingly precipitous which rose up there, a hill-like wall of rock...When one approached the edge of it, his eyes became unsteady; and if he wished to go forward in the same direction, there was no place on which he could place his foot; and beneath were the waters of a river called the Indus. In former times men had chiseled paths along the rocks and distributed ladders on the face of them...at the bottom of which there was a suspension bridge of ropes...

Of course, by no means all of the routes followed precipitous paths carved out of sheer cliffs. Had travel been only on such routes, that would have limited severely the volume of trade. Many mountain passes, while difficult because of the altitude, are in fact quite easy to cross, providing one is not caught in an unexpected storm. Safe travel across steppe lands might be possible in almost any direction, providing one did not lose one’s way and had the protection of the nomads through whose lands one might pass. It is no accident that the east-west steppe route from Mongolia through the pasture lands of the Altai Mountains or along the north side of the Tien Shan Mountains into what is now northern Kazakhstan was continually in use throughout Silk Road history. In many cases, the broad valleys were like highways pointing in just the direction a caravan might want to go.

Of course there could be key points whose fortification would permit control of travel—places where valleys between steep mountains narrowed or where the only route connecting wells or other sources of water might pass. We can see such points at the “Jade Gates” located at various moments in the history of the Silk Roads either at the edge of the desert in what is now Western China or in the narrow Hexi corridor, where mountain and desert constrict the normal route of passage.

To emphasize only the difficulties of travel and communication as seen from the modern perspective seriously underestimates the capacity of pre-modern people to adapt to their environment. They acquired or hired the expertise to be able to travel safely in difficult conditions. Travel might extend over long periods of time, broken by intervals where weather or local political conditions dictated that one stop. Most travelers covered only a portion of the “Silk Road”—those like Xuanzang or Marco Polo who went thousands of kilometers were the exception. Just as governments and local communities could control passage, they could also facilitate it by building bridges or caravan sarais, installing garrisons, or erecting markers to define a route though otherwise featureless terrain.

To a considerable degree, habitation and the flow of communication on the Silk Roads was hindered less by the permanent geographical realities than by the ephemeral conditions of war or peace. We know that one consequence of the Mongol invasions of Iran in the 13th century was to render certain areas uninhabitable due to the invaders' destruction of the irrigation systems, even though the Mongol rulers would later extend irrigation in the regions they considered to be important. There is a persuasive argument that the apparent decline of the overland trade in Inner Asia in the 15th and 16th centuries was less a consequence of the opening up of sea routes connecting East Asia with Europe and more a consequence of political instability which made the cost of safe overland travel prohibitive. The Florentine merchant Francesco Pegolotti, summarized the situation in the 14th century in this way:

The road you travel from Tana to Cathay is perfectly safe, whether by day or by night.... [But] there is [a] danger, when the lord of the country dies, and before the new lord who is to have the lordship is proclaimed: during such intervals there have sometimes been irregularities practiced on the Franks, and other foreigners... And neither will the roads be safe to travel until the other lord be proclaimed who is to reign in room of him who is deceased.

Photo galleries have been provided here to provide a sense of Silk Road geography in various countries. We hope eventually to add images from other regions and write separate essays using this visual material as illustrations. The photographs are provided courtesy of several photographers, who reserve their respective copyrights. Unless otherwise indicated, photographs are by Daniel C. Waugh.