In addition to being an artist, I do some writing, and noticing that my Age, Airbora, lacked that critical detail, I thought I might brainstorm here as to Airbora's origins....
Lets say Yeesha married.
Just as she wrote Relto for the new explorers, she wrote Airbora for her husband. A quiet man, he wanted a sanctuary, a place he could relax and write his own Ages.
Yeesha's husband was a skilled writer, capable of writing beautiful Ages, which is what brought he and Yeesha together.
The floating islands in the sky were the ultimate sanctuary, a concept learned from the Age of Serenia where certain rock formations levitated above the ground due to their magnetic properties.
Airbora, however, has no "ground" above which the islands can be levitated by magnetism. The exact properties of the islands are mysterious and their ability to float is unknown.
Harvesting certain trees on the floating islands, Yeesha's husband was able to build ladders, then bridges, and ultimately the dirigible with which he travels to distant islands that are otherwise unreachable.
Even after many days of travel, no direction seems to provide a sense of distance. There is no horizon. Only clouds and islands in every direction, yet they are all unique.