Trans-Siberian Railway from St. Petersburg to Vladivostok does not run across:

The Trans-Siberian Railway is the longest rail route in the world, stretching approximately 9,332 km from St. Petersburg in the west to Vladivostok on the Pacific Coast [1]. The route traverses the Ural Mountains, which serve as the natural boundary between Europe and Asia [2]. It also crosses major Siberian rivers, including the Ob and Yenisei [2]. While the railway passes through the southern Siberian regions and the Altai Mountains are located in southwestern Siberia near the route's path, the Caucasus Mountains are situated far to the southwest between the Black and Caspian Seas . Consequently, the Trans-Siberian Railway does not run across the Caucasus Mountains, as they are geographically distant from the northern and central Russian latitudes where the main line is situated .

Sources

1. [1] FUNDAMENTALS OF HUMAN GEOGRAPHY, CLASS XII (NCERT 2025 ed.) > Chapter 7: Transport and Communication > Trans–Siberian Railway > p. 58
2. [2] FUNDAMENTALS OF HUMAN GEOGRAPHY, CLASS XII (NCERT 2025 ed.) > Chapter 7: Transport and Communication > Trans–Siberian Railway > p. 59