Diagnose My City (Should be called Two-Face)

[stealingjoy 0]

Okay, I'm looking for some help/advice/pointers here as to why my city is the way it is.

As you can see, one half of my big city is looking quite healthy. Very few abandoned buildings. However the other half of the city is FULL of abandoned buildings.  However, the city itself is practically identical from one side to the other.  The adjacent cities to the north, west and east are also very similar to each other with relatively the same number of jobs and citizens (all the low wealth citizens are in the surrounding cities, while medium and high populate the main city).  It's been like this since the very beginning (i'm at roughly 900k population in the big city at the moment). Each side has the same amount of amenities roughly (obviously the more populated side has more hospitals and schools).One time, I went and demolished every single abandoned city because I thought maybe there was a domino effect, but it went back to being the same way.

$$$ Commercial (with some $$) is in a cross shape in the city with residential around it and a spot of industrial in each corner. There's heavy traffic throughout most of the region, as well.

Can anyone help me figure out why this is happening? It's bugging the hell out of me.

[jutrock 4]

i'm assuming you want help with the abandoned buildings? try mass transit like subways and stuff to try to get some cars off the road. lower commute times should help sims find jobs, which will keep them in your cities. i use lots of bus stops on main roads. variety shouldnt hurt either. try adding some lower density residential zones and suburban type commercial zones. no city is completely high density.

[stealingjoy 0]

I use a ton of mass transit. Barely 5% use cars. I have lower density residential in the neighboring cities... there's no demand for it in the big city.  I do know the basics.

I think I figured it out, though. I was artificially stifling my high density growth because of not building enough parks and so lots of medium wealth buildings were being built and abandoned since the demand wasn't really there for it. That seems a little odd but once I add parked, my high wealth population and building population went up. It seems I just overproduced medium wealth (even though there is still demand, which I also find odd).

Still, not sure why it would divide the city in half like that (which was basically what most confused me and was the point of the point... why half would be good and half bad if they're virtually identical).