Their route led them through Persia, along the southern and eastern shores of the Caspian (whose inland character, unconnected with the outer ocean, their journey helped to demonstrate), and probably through Talas, north-east of Tashkent.
Mounds of bones marked his road, witnesses of devastations which other historians record in detail; Christian prisoners, from Germany, he found in the heart of "Tartary" (at Talas); the ceremony of passing between two fires he was compelled to observe, as a bringer of gifts to a dead khan, gifts which were of course treated by the Mongols as evidence of submission.
It occupies a strategical position at the west end of the valley between the Alexander range and the Ala-tau (or Talas-tau), at the meeting of commercial routes from (1) Vyernyi and Siberia beyond, from the north-east, (2) the Aral Sea and Orenburg (connected with it by rail since 1905) to the north-west, and (3) Ferghana and Bokhara to the south.
In the valley of the Talas river he encounters the great khan of the Turks on a hunting party, - a rencontre which it is interesting to compare with the visit of Zemarchus to the great khan Dizabul, sixty years before, in the same region.
Of Tashkent, on the Talas river, at the western end of the Alexander range, its altitude being 5700 ft.