Awesome game buuuut...

So great game love it, its beautiful! However I seem to have all of my cities and 3 stars in each yet it seems like theres no where else to go! I was just wondering if Ive reached the limit or are there more maybe across the water idk? Also I cant upgrade iron tiles even though I have way to many and seems like I should be able to but it not allowing me

StardomFanatic about Train Conductor World, v1.3.1