Sometimes humans make something of which one says: You wondered if you could, but you never stopped to ask if you should. I think that's a quote from Jurassic Park.
Anyway, the Groningen Grid map (this is the updated second edition), is a city map-turned-subway map. Using the same rules as a diagrammatic transit map, all streets are angled either 0º, 90º or 45º. They still had to intersect roughly where they would in real life, but the lengths of the streets were secondary to where they intersect. So all the junctions are still intact - they may just be farther apart, or closer by, than in real life.
This resulted in a completely different look at the medieval city of Groningen. Where it is more curved and rounded, the city is now...