Once the season is over, the Kingdom reverts to being a regular Kingdom on the Global Map, just like any other kingdom.

Your seasonal progress then transforms into a post-seasonal game progress, which functions as a regular game progress.

After the end of the Seasonal Kingdom event, you will be able to teleport your post-seasonal City to an open Kingdom, should you wish.

To switch between progresses, head to the Progress section of the Account menu (the Main Menu in the mobile app). You can read more about this in the article entitled "How do I switch between my game progress instances (Cities)?”