First, your characters have so far lived their lives within a fairly large region known as the Solar Plains. Moderate climate, wispy clouds here and there but an otherwise clear sky most days, except for on the horizon. The horizon is shrouded in mist. Above the mist is what appears to be an absolutely massive dome that makes up the sky. At the apex of this dome is the sun. The sun is always directly overhead and there is no night time. Your characters have never experienced night time and do not know what a night sky looks like, nor do they even have a concept of stars. The sun takes up a massive 50% of the sky.
Within the Solar Plains are a variety of towns and territories that so far have always gotten along peacefully with an abundance of resources for all. Plenty of food, water, clothing and supplies, etc.
There are conflicts here and there, but nothing major such as war. At least not during your lifetimes, however long those may be.
The dome appears to be painted or carved, despite