Le Train Jaune (Ligne de Cerdagne).

First, the camera's own jpeg, resized to 900 pixels high.
Camera jpeg
Second, from the raw photo at 0EV.
0EV raw
Third, add +2EV for any detail in the dark bits (there aren't any shadows here).
+2EV for detail in dark bits
Fourth, subtract 2EV for any highlight detail.
-2EV for highlights
At last, use the "Three Exposures" filter.
Three Exposures
Sixth, G'MIC Local contrast enhancement filter.
Local contrast enhancement
Seventh, the Advanced Tone Mapping filter.
Advanced Tone Mapping
Eighth, use the curves tool for a bit more contrast.
Curve for contrast
Finally, sharpen with the GEGL Unsharp Mask.
GEGL Unsharp Mask