Improvement Triangles

[varus]

Couple questions:
I build farms in triangles because, like most, I've realized it's the best shape for maximizing their adjacency.
What is the technology that allows you to build farms -anywhere-? I've noticed that at a certain point in my games, I can build farms even on hills with no water... but I can't find the tech or civic or whatever that lets you do it. Is it an era thing?

I've heard people talk about triangle mines... what is that all about? Do mines get adjacency bonuses like farms? Is there a time/tech that this starts to happen? Can mines ever be build on flat tiles that don't have a mine resource?

 

[AgentDib]

Replaceable Parts (Tech): +1 Food Adjacency bonus for every Farm improvement Farms are adjacent to.
Feudalism (Civic): Farm improvements now gain +1 Food for each adjacent Farm improvement when 3 Farm improvements are adjacent to each other.

For some reason in Civ6 some important information for techs/civics only shows when you mouse over them. Maybe the Icon store ran out of icons halfway through.

 

[Xenotitan]

I don't think there's any point to triangle mines, and you can never build one on flat land without a resource.

Civil Engineering is the civic that lets you build farms on hills.

 

[Lord Yanaek]

I've heard people talk about triangle mines

I think some people simply believed mines work like farms and spread the word making more people build and talk about triangle mines, leading to more people thinking mines must be in triangle, leading to ... you probably got the point

Now, maybe some people call "triangle" mines the roughly triangular setup of 4 mines allowing 3 Industrial Zones in between