Frejus HO railway tunnel ferroviaire de Frejus. Mont-Cenis

Tunnel ferroviaire de Frejus, côté Italie
Frejus railway tunnel, Italian side
Traforo Ferroviaro del Frejus
Mont-Cenis 1871
Coordinates: 45 04 53N 6 42 33.4E

HO scale (1/87)
This is an artist view. Check my other models on thingiverse.com (phildc).

You could use Fuzzy printing to enhance surface aspect, as shown in the example.
Template.stl gives free space, and view of the surface
Cut3.stl is a small part to adjust the surface rendering in slicer software
test-all.scad allows you to check the parts, as this project is only a prototype.

The upper part is also available in 2 parts for the smaller printers.
Upper parts with -j suffix have holes for a joint between the parts.

Update:
The parts of the model are at HO scale.
A print test in N scale (1/160) was succesfull ( 55% scale): ref:
https://www.thingiverse.com/thing:6220426