Why are these only something found on the map and never something you can build?



Is this a balancing feature (too op to be able to build your own)?



Will it be possible to make a mod that makes them buildable?

tower foundations are like resource nodes once you research the proper tech (unlocked in era 2 same time the tower nodes show up)) you can place towers on those locations.



IIRC its the same tech that unlocks trade routes.

I think OP was aware of that, but is asking why they are that way. My guess is because there's no real system in place for building things on the map itself, apart from cities and boroughs.

The same reason why we can't manually change the direction of our roads. There are no worker units in this game to build stuff manually. We interact with terrain features using the city interface only OR parley/explore with armies.



Well, maybe if we could build tower foundations and change roads from the city interface... that would be interesting.

Although that would mean that there should be limits and maybe even upkeep to prevent spamming them everywhere.