|Hidden Palace Zone did not originate from fanon, and more information can be found on their respective wiki(s). You may read more about it on the following wiki(s):|
Hidden Palace Zone makes an appearance in Sonic Heroes 2. It has fallen into a state of disrepair due to the Echidnas clearing out into Mystic Ruins North and therefore the only habitant for the past 10+ years has been Knuckles. This changes upon Knuckles and Shade falling in love.