I've been trying to create a setting for my stories where the continent has only just recovered from heavy drought about a century ago and the various countries are rebuilding and fighting over food and so on.
I want to have a reasonably fast travel between the various city-states that dot the continent, and, at first, I figured steam engines were a good way to go since I didn't want carts or cars.
How do you get from city-states with limited resources to city-states with a reasonably good rail system. The trains doesn't have to work all the time; they just have to be at the point where they're generally the best choice for transport, despite occasional problems (bandits, breakdowns, track sabotage, etc.)
Also, since I will probably very loosely base the landscape on the many hills of Greece (since I got the city-states idea from them), remember that flat roads may not be common on this (section of the) continent.
The recreation of the steam engine is easy. All you have to have is metalworking and fuel, trees, coal, fossil fuels basically anything that burns will work.
A railway system is much harder. You need casting to make the rails. You need explosives to make tunnels. You need lumber for the ties. You need surveying to plan the route. You need a huge workforce to build miles of tracks. Then you need the determination to keep it going. Railways require a huge long term investment the famous transcontinental railway, the Union Pacific, cost an incredible amount and was a money pit for years after being built. Rails require constant upkeep most of the track will be ok most of the time but one loose rail kills everybody on the train.
Maybe you could approach it from a military standpoint. Like the Roman armies built roads your armies could build rails. Once the campaign is over the basic rail is still in place it just needs somebody to keep up maintenance.
Going with your Greece idea consider steamships/steamboats Greece is surrounded by water. Ports are hard to maintain (the same thing that makes a good harbor also causes it to silt in and become unnavigable). Canals also require maintenance but if the drought was severe enough you can claim they dried up and just became navigable again.