I have made earlier this thread but now i have made this thread in it i think of new idea:

In ancient to medieval era the first infrastructure is road which will give money by increasing trade and growth by food.

But in industrial era technology is very different and the attack can be fatal for us and a rough terrain will impact bad for troops.

So, i suggest if there is huge canyon and we want to cross it so instead of taking long route a bridge will be helpful to cross canyon and troop movement. It can be strategical important and enemy tries to destroy it.

If there is impassable tile we can create tunnel which will easy troop movement.

If distance between city decrease the economy will boost.

We can create railway line which will help in boost gold income and food transportation. This will also fast the troop movement.

To build railway line there should be station district and this can be completed by using production of both city.

I suggest troop movement from one destination to another destination to another.

For ex : city to outpost

              outpost to city

              city to city

              output to output

I also suggest upragradation of road like 4 lane or 6 lane which give realism and will increase migration, production and commuting workers from nearby city.

These are thing which shape civilization.