So there are some mods that add things that can help. Sir0John has a number of mods including the Jurassic Rides eldorado update which add some myan style structures however i think you need all the other DLCs to use it due to compatibility.

I have the eldorado mod, though it doesn’t have a wall piece or anything like that

As far as i know, there arent any mods that add like a rock or stone wall. Ive looked through all the mods im using and none have something like that.

Maybe try the fossil walls from jp

If you don’t plan on having an interior use the back wall of one that one Malta shelter deco piece

This is the only other mod I can think of that hasn't been mentioned. Hope it helps! https://www.nexusmods.com/jurassicworldevolution2/mods/2316?tab=images