The locations page has been updated! There's a toplevel for player-made locations where the shrine can be mentioned.

It may be difficult to upkeep wooden barriers or anything of the sort in the wilds, as Hilichurls tend to come and visit. We could handwave some open-air stone ruins in the cliff above the Whispering Woods. If Geo characters (such as herself) can close off gaps between the stone walls, it could make an enclosed arena with a partial ceiling.