Okay, so I've always liked fantasy landscapes showing islands floating in the air. And so I decided that I wanted floating big things (islands, castles, cities, etc.) in my new campaign world. But how to account for lots of big floating things? Well, one part of my campaign's Epic History is where the cryptic gods of the Yin and Yang emerged from obscurity to bring the world back into balance after it was ravaged by the warring Angels and Demons. However, they went too far and actually fell in to fighting each other and actually damaged the balance further. The ancient primordial gods were forced to return and impose a truce. Then the primordials forced the Yin and the Yang to erect reinforcing wards to restore the balance of yin and yang forces underpinning the world physically and magically. When the wards were completed they not only restored the balance but also strengthened the outer arcane barriers which cut off the portals to the home realms of the Angels and Demons.
These huge new wards were set floating in the air all around the edge of the world, with the four in the far corners of the world being larger and more powerful. The Yin and Yang gods called them pagodas to indicate their divine function. These huge warding pagodas were intricate constructions of stone, decorated and strengthened with metals and gems, and infused with either Yin (shadow) or Yang (radiance) power. Sixty-four of the massive pagodas were built, resembling huge floating shrines; half of them were Yin and half Yang, each marked with one of the 64 Yin-Yang hexagram glyphs.
Each pagoda has within it a soaring vaulted shrine containing a massive sacred stele with its particular glyph. There are also temple guardians, priests, monks, and other inhabitants. Each pagoda is led by an avatar of one of the Yin or Yang Conclave deities. The primary functions of the inhabitants are to perform holy rites to maintain the ward, and to worship and honor the associated god (Yin Conclave or Yang Conclave). The temple guardians include mortal creatures, divine creatures, spirits, and inanimate constructs.
However, the pagodas were built many, many centuries ago and a lot has happened to them since. Some are now a mere remnant, most of the structure blasted away. Others are shattered ruins, scarred and pitted by violent incidents of one sort or another. Many bear marks of conflict but continue to function as their creators intended. Some appear outwardly the same but have new occupants; one is rumored to now contain an entire town of sky-pirates.