After few busy days in Tehran we booked a train ticket for about 10$ each and travelled to the city of Shiraz. The train was quite comfortable but not very clean yet worth the experience. Ride a train in Iran and see it yourself!
Zagros mountain range and Alborz mountain range which most of Iran's population lives in are very green. But this part of the country simply doesn't have enough water resources.
Shiraz line is fairly slow I think. Iran is 90% mountains, so getting a decent alignment is neigh on impossible. There are/were plans to introduce tilt trains on the Tehran-Mashhad line (which has already been double tracked) which would bring it up to 200km/h from about 120-140kmh