each tunnel's portals will be custom made when necessary.
thus the northern portal of the gotthard tunnel itself has two tubes at the entrance which join and become one after a very short distance.
if so inclined, you can watch a cab ride video of the journey through the whole 15 km long tunnel on alpentunnel.de.
the video called "Führerstandsfahrt Amsteg - Airolo" of course not only covers the ride through the tunnel, but also the climb up from erstfeld to göschenen.
here is a direct link if you do not speak german, be careful its 362 mb.
