The Trans-Iranian spans 1392 km / 865 miles from the Persian Gulf at the port of Bandar-e Emam Khomeyni (known as Bandar Shahpur before the 1979 Iranian Revolution) to Bandar Torkaman (formerly, Bandar Shah), a port on the Caspian Sea, via Tehran, passing two 2000 meter-high mountain ranges. Inaugurated in 1938, it was built by two successive consortiums with Danish-Swedish Kampsax leading the construction of the mountainous sections. The works were completed by many Austrian, German and Italian subcontractors. This explains the German or Swiss look of the line bridges, tunnel portals and masonry artifacts. During WWII, the British, American and Soviet armies intensively used the line to carry military supplies north to USSR from and though non Axis-occupied regions (the “Persian Corridor”).
The picture shows a southbound empty tank train in the Zagros mountains between Andimeshk and Doroud, near the remote station of Shabazhan, 602 km south of Teheran by rail.
Thanks to the screeners for granting this picture a "Screener's Shot" prize. Looks like they like this location, as they also granted a "Screener's Shot" to a picture of the same bridge taken from the opposite side. See here: RPN picture #577130.