City of the Anemos
The City of the Anemos is the fandom term for a city that is described in Golden Sun: The Lost Age as the city that formerly occupied the gigantic crater located right next to the settlement of Contigo on the continent of Atteka.
As gossip and Mind Read dialogue in Contigo (both before and after the Jupiter Lighthouse is lit) reveals, the Anemos culture was a great culture of Jupiter Adepts that had the Psynergy-based power of flight, and were based in this city. At some point in Weyard's ancient past during the Alchemy-based wars, a disaster had befallen the Anemos, which according to gossip had something to do with the flames of the four Elemental Lighthouses being put out. So, something rather fantastic happened: The city lifted up off the ground and rose into the sky, leaving a giant crater (referred to as the Anemos Crater) and sparse remnants of the Anemos culture behind, and began to float through the sky far above ground from then onwards. If the gossip is to be believed, this is the true identity of Weyard's "moon", as people on the ground have looked upon the floating landmass' underside over the ages. But while most of the people on the ground at Weyard have long observed the moon in the sky, apparently only the remaining descendants of the Anemos based on modern-day Contigo are aware of what is actually on it.
Popular fan theories make the assertion that this "floating city in the sky" has to do with Sheba, who is described in the first game as having fallen from the sky as a baby and landed near the town of Lalivero with the impact of a meteor but without any bruises at all. It would be entirely plausible that a baby Sheba had fallen off the floating city in the sky (or was perhaps "sent down" from the city to the world below).
Connection to Werewolves
The werewolves of Garoh automatically transform into their bestial forms whenever they look up at the full moon at night. Why this transformation would occur to these people upon looking at the moonlike underside of this alleged floating city is, of course, never explained or explored in the Golden Sun series as of the present. Strangely, the werewolves of Garoh have a connection to Jupiter Psynergy (probably from the nearby Air's Rock), as did the Ancient Anemos who supposedly inhabit the topside of the moon.