I was looking at some maps for a future article and saw something interesting about Italy.

The Po River Valley is the richest and highest-density area because it's the most fertile.

But then there's this line of cities. That's so weird. Why?

So I turned to look at what's there, and a bunch of cities are on a near perfect line! From Piacenza to Rimini through Parma, Reggio Emilia, Modena, Bologna or Forli.

They're all connected by the E45. So I wondered: What's the history of E45?

Turns out it was the Via Aemilia that Romans built to control the Po Valley.

They built it on the mountainside of the Appenine Mountains, as straight as they could for efficiency, and then built cities along its way!
https://en.wikipedia.org/wiki/Via_Aemilia

In fact this can still be felt in other places.
Look at the roads in Spain
(Made a gif from @xruiztru 's images)
https://twitter.com/xruiztru/status/1360499526482681862?s=20