Hello.
I have a city for sale. It's far from the core of my empire (that's why I am willing to give it away). I conquered it from another civ because it contained the GLib. But now the GLib is obsolete, and the city fully corrupt, so it's no use for me. Still, it's a nice city with beautiful surroundings.
But strangely, no other civ wants to buy it, even for 1 measly gold.
Is there any rule prohibiting to sale cities?