Good insight and thanks for adding to the topic. What I mean however is I have noticed those 'seeds' so to speak to change, maybe once a day or so (I haven't mapped out a science). I am still testing some things out before I say anything certain but I think the date has some effect to it. Anywho I am adding a video of me running through all 4.
I got the tall 'Willy Wonka' room in one of the cities, and out of 4 portals I got 3 cities which I thought was pretty good. I have gotten none all the way to all 4 in the past. Also goes into what loot you find where and some other details.