Le Train Jaune (Ligne de Cerdagne).

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