Golden city is a legend introduced in Final Fantasy XIV. It was believed it was hidden somewhere in Tural.
Origin of the legend
The legend of the golden city originated from the Yok Huy, a people of giants, who once ruled Yok Tural holding all other races under their heel. Yok Huy dreamed about the city of gold where people lived in an eternal happiness, and in the middle of the city was a statue of a goddess.
Yok Huy began to expand to Xak Tural to find the golden city. Their conquest ended in disaster when a disease started spreading among them. While the disease was fatal to Yok Huy, other races were either immune to it or only suffered mild symptoms. Yok Huy retreated to their homelands in Urqopacha, and their conquests ended. From that moment on, the Yok Huy never again dreamed about the golden city.
The Ascians were aware of the legend, and in his final moments in Ultima Thule, Emet-Selch suggested the Warrior of Light to see the fabled golden cities of the New World for themselves.
The truth
In truth, the golden city is Living Memory, a place in another reflection of the Source. Long ago, the kingdom of Alexandria existed within this reflection. When the reflection became covered under constant thunderstorms and everyday life became a struggle, a black ore called electrope was discovered, capable of absorbing lightning energy. When it was imbued with arcanima, it could transform lightning to other elements. Electrope became a salvation for the world, but it soon brewed a war that came to be known as the Storm Surge, when all the nations desired more of it. The war saw the kingdom of Alexandria fall to ruin, and after the neighboring kingdom of Lindblum activated a superweapon that caused lightning to run rampant across the world, life within the reflection was lost.
Alexandria survived thanks to the efforts of a group called the Preservation who used electrope to cover Alexandria within a dome that kept its people safe from thunderstorms. They used electrope to extract souls from the deceased, then extracting memories from them, and then storing them for future use. A massive 12-level structure called the Everkeep was constructed with electrope. Levels 1–11 were used by the living in various ways, but the top twelfth level was Living Memory. Here, the Preservation used the memories extracted from souls to create facsimiles of the deceased Alexandrians, where they would "live" eternally in happiness. These facsimiles were called the Endless. The place was constructed with electrope and utilized in such a way that it would mirror Alexandria at the height of its existence. It had golden hue and in the middle of it stood Meso Terminal, which was constructed with an image of Alexandrian Queen Sphene. The place very much resembled the Yok Huy legends about the golden city.
The entrance to the golden city was constructed with electrope within Skydeep Cenote in the forests of Yak T'el in Tural. The purpose of this gate was to open a way to the Source so that the Preservation could steal living aether from it to maintain the Endless, since they required a constant supply living aether from living souls. The gate was opened only once before the events of Final Fantasy XIV: Dawntrail.