I found an area that looks rather similar to this that I got to from the industrial maze underneath the Mansion.
There's even a creature that looks similar to the sunken sun statue (http://i.gyazo.com/f3ca5f8cc658678eca17b96cd71139e4.png)
Does anyone have any ideas? I've been tenatively calling it the Overgrown City cuz that's what it sort of looks like to me.