Also newer or rebuilt cities like Rotterdam would be interesting as well I think. Also since Europe is more dense than America there might be some different opinions on how things are to be planned.
One thing that really surprised me when poking around Google Maps a while back is how griddy Weimar is compared to other European cities. While the downtown is a mess, the areas immediately outside it are on a grid that wraps around the city.
Most European cities have grids but you have to "zoom in" a lot. And those grid "pieces" aren't themselves arranged in grids. So there's usually very little continuity for the grid pattern over distances. The direction tends to change every few streets.
So in most cities if you zoom in on the map you'll see mostly grid-like patterns. But as soon as you start zooming out it fades away into a mash of directions, turns, and swirls. The only places where it's hard to find any kind of straight line is in (centuries) old city centers.
I don't find Weimar particularly "griddy" compared to any other city.
P.S. Barcelona is the "griddiest" big European city I know. Even though at some point the grid changes alignment they have huge chunks with almost perfect squares between streets.
Barcelona is particularly awesome in this respect. Historically, it was a few distinct villages. Then during a period of growth each of those separate areas were connected by a modern (at least at the time) grid. Looking at this area on google maps is fun. You can scroll between two adjacent zoom levels to see modern gridded order vs the total chaos of a gothic village (looking at the gothic quarter or vila de gracia in particular).
When I visited, I was confused about how the city was configured so oddly until I saw a pre-modernization map, then everything suddenly clicked.