You may or may not remember, but a while ago i claimed a plaza tile in one of my cities vanished. while at the time i could not understand why this could have happened, i decided to test to see if i could produce the same result:
I first checked that my version of pharaoh had no bugs to do with plazas, checking that plazas did not devolve when near undesirable buildings.
My tests turned up two positive results of when plazas disappear.
Firstly, when a festival square is placed over plaza tiles, they not only disappear when the festival square is deleted, but also loose their desirability. even when under a roadblock plaza tiles keep there desirability.
the second occasion when a plaza disappeared was when a roadblock was placed over it, then set on fire. however i don't think this counts entirely as not only the plaza tiles but also the road was destroyed in the fire.
these were the only two occasions in which plazas disappeared and lost their desirability in my tests. this may not be the only times it happens but were the only occasions on which it occurred in my tests.
I first checked that my version of pharaoh had no bugs to do with plazas, checking that plazas did not devolve when near undesirable buildings.
My tests turned up two positive results of when plazas disappear.
Firstly, when a festival square is placed over plaza tiles, they not only disappear when the festival square is deleted, but also loose their desirability. even when under a roadblock plaza tiles keep there desirability.
the second occasion when a plaza disappeared was when a roadblock was placed over it, then set on fire. however i don't think this counts entirely as not only the plaza tiles but also the road was destroyed in the fire.
these were the only two occasions in which plazas disappeared and lost their desirability in my tests. this may not be the only times it happens but were the only occasions on which it occurred in my tests.