[Tiffany]

I got curious and looked up Final Fantasy X on Wikipedia, and found this:

Originally Posted by Wikipedia

At Yevon's order, most of the surviving common citizens and summoners of Zanarkand gave up their lives to become fayth, whom Yevon would then use to conjure a summoned form of Zanarkand, using their memories as the basis for this massive summon. This summoned replica of the city was to be an ideal paradise, removed from conflict and those who may infringe upon this city of memories. This summoned version of the real Zanarkand is sometimes called "Dream Zanarkand"' to differentiate it from the original Spiran city which has been lying abandoned in ruins for the last one thousand years.

In order to accomplish this, [b]Yevon manifested the city out at sea in an undisclosed location, far removed from the Spiran mainland and the warmongering Bevelle. Further, to prevent technology from allowing Bevelle or anyone else to easily locate his summoned city, and to protect himself while he summoned it, he created a magic armor. Yevon used gravity magic to surround himself with pyreflies and used them to create an invincible armor that would terrorize Spira for one thousand years: The monster known as "Sin."[3][4][b] This armor would not only protect Yevon while he summoned Dream Zanarkand, but he also "programmed" it to attack areas with high populations and advanced technology, thus, bringing technological progress to a halt and keeping the people of the mainland from giving much thought to what may lay far out at sea.

Hope that helps a bit. I never knew that about Sin.