I was in a group doing Fungal Grotto II, and we found a lot of interfering collision. Some of it prevented or blocked movement, messed with the camera, etc. After we defeated the final boss, we did some probing, and was able to actually start climbing it by hopping around the one Redguard NPC. It feels like it may be roughly mushroom in shape for the largest by the wayshrine. There were two other instances over by the little camp area where you get the quest that weren't as tall, but definitely still lifted you in the air or blocked your movement.
Probably not a good thing to have things like that in a boss-fight arena...
We left a bunch of /bug reports, but they may be a bit disjointed. Each included screenshots, though, and we have some more. It's possible to use Shards and Caltrops from up there to have the ability floating along with you.
Not sure if this is exploitable. Probably not, considering the boss mechanics of "go into the dome" and such. Further testing needed. Screenshot example below. Hope this helps.
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