“The Stone Tower: Ptolemy, the Silk Road, and a 2,000-year-old Riddle” by Riaz Dean

Ptolemy's Stone Tower on a 16th-century map Ptolemy's Stone Tower on a 16th-century map

“One might ask,” begins Riaz Dean in the introduction to his new book The Stone Tower: Ptolemy, the Silk Road, and a 2,000-year-old Riddle, “how this book is different from the many others about the Silk Road.” How indeed? “At its heart,” he continues:


it attempts to solve a 2,000-year-old riddle of ancient geography: Where was the now-lost Stone Tower that Ptolemy spoke of, which marked the midpoint on the old Silk Road as caravans plied their trade between Europe and Asia?


Ptolemy “mentions it ten times in Book I” of his Geographia:


and with a familiarity that suggests this was a well-known and established landmark. Frustratingly, though, Ptolemy fails to describe it further, not even a hint as to whether it was a settlement, natural feature, or perhaps a solitary man-made structure.


Something of a historical adventure story, then, without knowing quite what one is looking for. The prominence of the Stone Tower in Ptolemy has meant that explorers like Ariel Stein have been looking for it since the 19th century. Various places have been proposed over the decades, from Tashkent or Tashkurgan in western Xinjiang (early favorites of the medieval Islamic scholar al-Burani and Stein respectively), both of which have names which approximate “Stone Tower”, to Daraut-Kurghan and Osh, both in what is now southern Kyrgyzstan; the latter’s claim comes from being the site of the sacred mountain of Sulaiman-Too which rises abruptly from the surrounding landscape, a metaphorical rather than actual “tower”. Not wishing to give the mystery away, suffice it to say that Dean makes a pretty good case.

Ptolemy is someone today’s readers might be less likely to have come across.

The Stone Tower: Ptolemy, the Silk Road, and a 2,000-year-old Riddle, Riaz Dean (Penguin Viking, February 2022)
The Stone Tower: Ptolemy, the Silk Road, and a 2,000-year-old Riddle, Riaz Dean (Penguin Viking, February 2022)

This mystery itself takes up only a couple dozen pages or so, and Dean has prefaced it with a discussion of the history of the early Silk Road, interspersed with fragments of a fictional story of a nomad family, as well as an introduction to Ptolemy’s Geographia.

In the former, Dean weaves history with narrative, contemporary accounts and a reader-friendly approach to story-telling—but there are other accounts which are more strictly historical, such as Christoph Baumer’s photograph-laden and encyclopedic The History of Central Asia: The Age of the Silk Roads and Peter Frankopan’s The Silk Roads: A New History of the World. Readers have a choice.

The latter, since Ptolemy is today perhaps less in fashion than he was when such 19th-century explorers as Heinrich Schliemann used to carry copies of the classics as guidebooks, is however something readers might be less likely to come across:


… an extensive gazetteer which makes up the bulk of Geographia (Books II–VII). In it he lists some 8,000 place names and their coordinates within the known world.


Ptolemy gave coordinates in latitude and longitude based on his own schema; neither was possible to measure directly and hence coordinates are all approximate to a greater or lesser degree (which is why the possibilities for the Stone Tower’s location are hundreds of kilometers apart). Ptolemy was, furthermore working off hearsay:


The basis of Geographia, as we know, was the lost work of Marinus of Tyre, who in turn obtained much of his information about Asia from the trader named Maes Titianus and his caravan …


Dean provides an interesting overview of Ptolemy’s methodology and thought-process in assigning coordinates to the Stone Tower and other locations.

This story isn’t over.

Dean, as do his predecessors in this quest, assume on Ptolemy’s authority that the Stone Tower existed. Yet Ptolemy’s information was at best third-hand and there is no independent corroboration. There are apparently no corresponding mentions in Asian sources, nor do any of the places in contention map onto a site with a clear archeological record of being the sort of major trading post that the narrative indicates that it was.

Less romantically, but more perhaps significantly, identifying the Stone Tower with certitude might nail down many other as yet unidentified places in Ptolemy’s Geographia. Since one supposes that relative locations are more accurate than the absolute coordinates, Dean explains


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 … 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.


Whether the rest of the coordinates can now be mapped onto identifiable places would, failing clear archeological evidence, be the real test whether the choice of location is correct.

The story of Stone Tower seems more or less at the stage the search for Leif Ericsson’s Vinland was before an actual Norse site was identified at L’Anse aux Meadows: possible, even reasonable, but still conjecture. This story isn’t over.

Peter Gordon is editor of the Asian Review of Books.