I'll be remembered much better
as the bad person that won't share
his ideas I believe

Look on the posts.
they'll remember me for very long.
he he he
OK. Now how to put a city on a city.
the clue is that you must changeterrain
the city by events. But in a specific way.
usually when you changeterrain city,
it is destroyed. But not always.
It is a bit complicated.
Now watch carefully.
..
@.
..
@ is a city,
. is some terrain.
You must changeterrain those rectangulars
that will be now shown as $;
.$
@$
.$
I mean, a vertical line of rectangulars
(haven't tried with horizontal, but it probably would work too)
next to the city, not the city itself.
f.e.
if a city is on spot 128, 68,
make changeterrain event like that;
129,67,129,67,129,71,129,71
Now the city will be changeterrained by this event too.
You can't see it.
But unlike in normal changeterraining,
you'll see its name still on.
Now create a settler on the city.
And a second one.
the first one is hidden somehow, though it exists,
but the second one is on. Set it to build city,
and changeterrained city will appear again.
But note, with the name of founded by you city,
and colour of your civilization.
This city you can open only by attitude advisor.
As long as I'm right, it can't be cityedited.
But it can't be conquered too. If the upper, primary
city is captured, the hidden city remains in owe
of the same player.
the sad thing is that you can't change the size of it,
only by allowing it to grow.
Note, the spot on which the city is founded,
is shared by both cities. But other are not.
So the spot should give at least 2 food.
If the hidden city starves, we come back
to the situation from before founding the city.
I believe that would be the difference from
hex-editing way. Negative one.
I don't know if there are any positive differences
simply because I have never hex-edited anything.
Now how can we use that?
-nations. F.e. In ottoman
Empire, hidden Greeks, Serbs etc.
-what comes after it, partisants.
Under objective cities, there are
hidden cities of revolting nation,
and your aim is to build up such
a nice force in them to struck oneday
and take them.
-social classes, religious or work groups.
F.e. bankers or Copts in Egypt; if you treat them
good, they'll give you money etc.
-mercenaries recruiting.
Under the capital of civ
there can be a hidden city,
set to build a mercenary.
If you disallow opening attitude
advisor, human player won't know
from where he got them.
-it allows to make a small nation
economically- or military- very strong.
Imagine, 100 cities one on another,
in every of them a bank, a marketplace...
And bunch of trade routes.
etc
As you were all bad to me,
I won't share any other ideas or discoveries until
I'll release some scenario ;-P
Of course if you believe I have any.