The quest to find the Stone Tower has gained momentum through the ages and, in the process, generated much “spilt ink” – but to what purpose, one might ask? The answer lies at several levels but simply put, it was the most important landmark for travellers along the Silk Road.

Both geographically and figuratively it represented the heart of the overland trade network, and was a halting place that Ptolemy referred to frequently in his Geographia. Of itself, this makes its search worthwhile and almost needs no further justification.

Here, caravans moving between Europe and Asia would break their often long and arduous journeys to allow merchants and other travellers to rest, trade goods and take on provisions before continuing to the next stage.

In modern times, the interest in this Eurasian network has been steadily increasing ever since Stein and others initiated the concept of Silk Road Studies around the beginning of the twentieth century. The second phase of this scholarly field started gaining impetus in the 1980s, spurred on as Central Asia became more accessible to visitors across what was once Turkestan and which, until recently, had been split into Russian and Chinese halves.

The western Soviet half then comprised the now independent five countries ending with stan (meaning “land of”), while across the Pamirs still lies the Chinese half represented by the massive but sparsely populated Xinjiang province. Tourists have recently begun travelling the length of this timeless caravan network in increasing numbers, seduced by its evocative images and historic sites, keen to experience its myriad of people and cultures.

As a marketing tool, “the Silk Road” phrase is frequently employed in a multitude of ways and across many countries, to the point where its historical legacy is now blurred by metaphor.

Described as the world’s earliest highway, acclaimed cellist Yo-Yo Ma has gone further, labelling it “the internet of antiquity”. In 1998, he founded the Silk Road Project, a not-for-profit organisation which celebrates the living arts of peoples along this network. Four years later, his ensemble played at the Smithsonian Folklife Festival in Washington DC, an event which hosted well over a million visitors that year under the banner The Silk Road: Connecting Cultures, Creating Trust.

In a more permanent way, the International Dunhuang Project strives in its mission “to make information and images of all manuscripts, paintings, textiles and artefacts from Dunhuang and archaeological sites of the Eastern Silk Road freely available on the Internet”. UNESCO, in particular, has worked hard to promote and institutionalise this second phase through a great deal of research and literature, including its initial ten-year project Integral Study of the Silk Road: Roads of Dialogue begun in 1988. To date, it has designated over a dozen Silk Road sites on its World Heritage List, although a possible listing of the Stone Tower still eludes it for want of proof.

Even before Ptolemy’s time, from the shores of the Mediterranean all the way to the Greek colonies of Central Asia, the country and its settlements were relatively well known to the ancients, but eastwards from Bactria the geography became increasingly vague.

In one of his maps – the one containing the Stone Tower – Ptolemy also stated the location for over one hundred towns and physical features, but the coordinates he left us were approximate at best, as will soon become evident.

If his midpoint of the Silk Road could be pinpointed, then this would certainly lead to other pieces of historical geography and cartography falling into place. Identifying a likely location would also allow future archaeological work at other sites in this vicinity to be more targeted, thereby increasing the chance of successful excavations and the discoveries that would surely follow.

Kang pulled his peaked cap closer around his ears and tightened his knee-length coat about his waist to ward off the morning chill. Yet he still felt the cold and tiredness in his bones. It added to his growing weariness from the responsibility that came with the title Sabao, which set him apart and somewhat alone as the leader of a caravan.

More and more nowadays, during the long marches he found his thoughts drifting back to seasons gone by and the many trails taken. He stroked his almost-white beard, remembering well the times with his father and their blood relatives from the steppe, whom he saw less of now. Once the route through Ferghana had become safer and well-trodden he, too, had favoured it above others.

After his father was crippled while taming a wild horse, there seemed little value in keeping the stud farm. So, he had moved the whole family into Samarkand, including his widowed daughter and her children, whose husband had been knifed in a dispute by a dry well deep in the desert. Their town, stretching along the wide and lush valley, was growing steadily and its many irrigation channels off the Zerafshan River had proved a boon for farmers. He had staked out his land at a good time, when its location along the caravan routes made the most of the plentiful trade during these peaceful times.

Although his books have survived, of Claudius Ptolemy the man almost nothing is known – what little there is must be inferred from his own writing, but this leaves no doubt as to his genius.

“He stands like a colossus astride the ancient world, and his influence is still felt today” according to antiquarian map authority RV Tooley, who goes on to add: “His Geographia dominated the whole of the Christian and Moslem world for 1,500 years.”

JW McCrindle, while translating sections of Geographia for his text Ancient India as Described by Ptolemy, described him as “a Mathematician, a Musician, an Astronomer and a Geographer... altogether one of the most accomplished men of science that antiquity produced”. But with this great stature came an inherent problem: Ptolemy’s theories often went unchallenged, and his cartography remained unquestioned for centuries.

So much so that he both inspired and misled Christopher Columbus into discovering America: The existence of both American continents was unknown at the time; after having consulted his work, Columbus serendipitously sailed west in the belief that he would find the riches of Asia when he next made landfall.

Neither the date nor place of birth for Ptolemy has ever been positively established. Born around AD 90, he was a citizen of the Roman Empire who resided in its Egyptian province and its capital Alexandria, located on the Mediterranean within the Nile delta. Founded centuries earlier by the conqueror whose name it bears, this city was second only to Rome within the empire; and home to one of the finest institutions of the classical world, the Great Library of Alexandria – thought to have contained almost 500,000 books at one stage. (It has been said that, if the Jews were the People of the Book, then the Greeks were a people of many books.) In this library, Ptolemy would have undertaken his research, drawing on 400 years of scholarship by other great Greco-Roman thinkers.

Nearby was the city’s thriving port, the largest in the empire, from where all manner of goods emanating from the Silk Road were shipped to and from Rome. Not only was it heavily guarded, but all crew and passengers were scrutinised and required to hold passports to enter or leave the enclosure. Often their luggage was searched for texts; and if any new or foreign books or manuscripts were found, they were promptly confiscated and copies made out by hand. Eventually, a copy was returned to the owner while the original was added to the library’s collection.

The Stone Tower: Ptolemy, the Silk Road, and a 2,000-year-old

Excerpted with permission from The Stone Tower: Ptolemy, the Silk Road, and a 2,000-year-old Riddle, Riaz Dean, Penguin Viking.