The start point of travel is no doubt – is a modern city Sudak in the Crimea.
Next Rubruk rode two months to the Sartach's court. He specifically said that was driving very slowly and could be overcome this way for a month if had gone horse riding. Thus, the distance to the Sartach's court was 900..1200 km.
In this section we have the following landmarks: Perekop (165 km from Sudak); coast of the Azov Sea (420 km from Perekop to Taganrog); somewhere near modern Taganrog (the exact location can not be established, but it does not matter for us) travelers abruptly turned north, crossed the Seversky Donets (this turn and crossing not recorded by Rubruk, there is only a general mention that on the way they crossed the many rivers) and came to the Don shore.
The crossing was provided Ruthenian settlement, which name was not mentioned. Its place was not close to the Don's mouth, as Rubruk writed that ambassadors traveling in winter went by south way and crossed Don below the place where he crossed.
I think that Rubruk crossed Don somewhere at the beginning of the great Don bend, near modern Boguchar (330 km from Taganrog).
When it was – certainly not stated; Rubruk said only that it was before the feast of blessed Mary Magdalen. I assume that in the day st.Mary (July 22, 1253) he went from Don further to east, and three days parking at the Don in this case fall to 19 – 21 July.
It turns out that during the June 9 – July 19 (40 days) Rubruk overcome distance 830 km, giving an average speed of 41 km per day.
Beyond Don travelers had to take a course to the northeast and in 9 days, covering about 360 km, got in a Sartach's headquarters. If my reasoning is correct, this headquarters should be located somewhere near the modern city Atkarsk (Saratov region).
Why do I think so? First, based on Rubruk's mention that "country beyond the Tanais is most beautiful, with rivers and forests" (chapter 16). Indeed, the road from the Don to the Volga, he had to cross the larger rivers such as Hopper and Medveditsa. Rubruk clearly distinguishes the above-mentioned forests from the great forest, which lies to the north. This forest meets the natural forest area, and Rubruk's way passed in forest-steppe. Unfortunately, I cannot found detailed map of natural areas of European Russia; on the general map shows that the southern limit of forest-steppe area is approximately along the line of Voronezh – Saratov, ie calculated by my place of Sartach's court is just on the edge of the forest-steppe and steppe.
Second, having left from Sartach, Rubruk already on the third day reached the Volga. That this headquarters was for 100..120 km from the Volga. From Atkarsk to Saratov (on the Volga) only 75 km – distance, which indeed can be overcome by 2.5 – 3 days. If we assume instead Atkarsk location of headquarters in the Rtyschevo or Balashov, these places remote from the Volga River 180 km.
"Traveling then due east toward Baatu" – recorded Rubruk. If one treat the expression literally, from Atkarsk to Volga coast near the modern village Voskresenskoe – 120 km, but if one take the direction to the southeast, to the banks of the Volga near Saratov is 75 km. Of course, to trace route in such detail we have no landmarks enough. Therefore, we believe that the ferry across the Volga River took place near Saratov, where Rus-Saracenic settlement was arranged to provide the crossing. N.P. Shastina in her comments said that this should be Golden Horde city Ukek, site of which is located on the outskirts of Saratov. This identification, as we see, may be accepted.
Next Rubruk's note – "from that place to the cities of Greater Bulgaria to the north there are five days" – is incomprehensible to me. Even if we assume with great reserve, that "the southern cities of Bulgaria" reached the beginning of Samara bend (near the modern city of Togliatti), the distance from from Saratov go straight will be 330 km, and skirting Samara bend by left bank of the Volga – 420 km. A more realistic view, I believe that "the southern cities of Bulgaria" were near the modern town Tetyushi (not southward), that is another 150 km to the north. Distance from Saratov to Tetyushi – about 570 km, which exceeds the 5 days, specified bt Rubruk.
In the Volga travelers found that the Batu's court in their movement has gone south crossing, they overtook the headquarters, sailing down the Volga. Duration of sailing Rubruk did not mentioned, obviously it was not great. Then Rubruk together with the Batu's court entire 35 days was moving south along the Volga.
For the place where Rubruk left Batu's court, we can assume that it was not for the south of modern Volgograd hydroelectric power station. Further south Akhtuba is separated from the Volga. Rubruk described in detail these sleeves of Volga, when returning back, but on the way to the east, he did not mention about them. From this we can bring that Rubruk traveled down the Volga (water and shore) from region of Saratov about 300 km away; speed rate is about 8 km a day.
Leaving from Batu, Rubruk after 12 days arriving to the river Yaik (Ural). If he move exactly to the east, it is 480 km, and average speed – 40 km a day.