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.
While still young he started on a pilgrimage to Jerusalem, and travelling by way of Tangut, Khotan, Kashgar, Talas in the Syr Dania valley, Khorasan, Maragha and Mosul, arrived at Ani in Armenia.
The west continuation of the Kunghei Ala-tau is the Alexander range, which in its turn bifurcates into the Talas-tau and the Kara-tau, this last stretching far out into the desert beside the Syr-.
From the middle of the Alexander range, in about 74° E., a chain known as the Talas-tau breaks away from its south flank in a W.S.W.
The Talas-tau, sometimes known as the Urtak-tau, while the name of Ala-tau is also extended to cover it, has an average elevation of 14,000-15,000 ft., but lifts its snow-capped summits to 15,750 ft.; it is crossed by passes at 8000-10,650 ft.
It is not clear, however, whether orographically it is connected with the Alexander range or with the Talas-tau.