[Darth-Apple]

For me, it was around 180K. I couldn't get past that. I was using 7 tiles, and my poor little computer could not keep up any longer. The frame rate was about 2-3 FPS by the time I finally gave up on it. 

What is the largest city you've created in Skylines (or in Simcity)? Please specify which game you are playing when posting!

[Guardian]

I JUST cracked 100k, then immediately stopped playing one. I had grown bored with it, but at just under 90k, I had to see it through to 100k. I've been thinking about making a new city to try and build up, but I always feel like I mess them up and tire of them.

[Darth-Apple]

It gets to the point where the core of the city is done, and the rest of it is just expanding around it. I find myself creating mini sub-cities and then trying to jam the interstates as much as possible with traffic in between, but I'm much like you. I just get bored of it after a little while.

I don't know how some of these youtube streamers have the attention to detail that they do. Some of them have really made some fantastic looking cities.

[Guardian]

Truth. Mine tend to just become sprawls to the point where traffic grinds to a halt and I spend most of the time trying to fix that without being unrealistic.

[Darth-Apple]

I have to cheat past about 150K and use a demand mod for that very reason. CSL very oddly has an issue where, once the attractiveness of your city goes up, commercial demand skyrockets, but residential doesn't go with it. You end up with too many jobs and not enough workers, and everything just grinds to a halt.

[Kyng]

I got up to about 98k on my largest city, then I got completely stuck there, despite the fact that I was still physically expanding the city outwards. It actually made me wonder whether the population was capped at 100k (which, on my machine, I suppose it could have been for performance reasons).

I'll have to get back to my current octagonal city at some point, though, to see how far I can get with it .

[Darth-Apple]

It's not capped at 100K, per se, but the demand kinda borks it once you get around that level. You end up with very limited residential demand which makes it very hard to grow larger.

The primary two things I realized that would make a difference were 1) Traffic, and 2) a demand mod. The demand mod is cheating, somewhat, but making sure traffic flow is great tends to be very good for helping out at least somewhat.