Is the City of Gold real?

I assume you're talking about one of the legendary "Seven Cities of Gold", in which case the answer is "there's no evidence that there ever was such a thing."

Francisco Vasquez de Coronado went in search of these, two of which were named Cibola and Quivira. Coronado eventually found Cibola, which turned out to be a bunch of adobe pueblos with no gold at all, and while there learned the location of Quivira, which he set out for, but likewise, when he got there, it was just thatched huts and one smallish piece of gold, which might even have come from one of the men in his own expedition.

There was a noticeable pattern to stories of the "City of Gold." It was always "Nope, not us, white man, um, which way did you come from again? Oh, right. As I was saying, the City of Gold is that way, the opposite direction from which you came, over those hills there." It seems reasonable to conclude that the stories were motivated at least partly, if not entirely, by a desire for the Conquistadors to go conquist somebody else.