In Ustengrav Depths main cavern there seems to be a treasure room that can't be reached, or at least i have not found the pathway to it. On the side of the cavern with the Throne and Seated Drogre and the burning drogre (serves as the flame trap warning) up on that upper level there seems to be an additional treasure room. If you go right after passing our burning drogre almost to end of passage, or whatever you want to call it, there is a section where things have collapsed and you can see past the broken columns and vines into the passageway beyound. If you look carefully you can see a large chest, a dead drogre, a soulgem, and the usual candles, torches, etc.

Has anyone actually found a way to get into that section and collect our loot? From down in the main cavern if you look up you can see a bridgeway from that area over to one of the central pillars, but then all other connections are trashed and I can't locate any drawbridges or other means of connecting to that pillar.

Thanks

I don't recall specifically, but I know I've been there and I'm pretty sure I've cleared every room of every dungeon.

Wikia mentions this:

I'm not sure about Ustengrav but in some caverns you have to jump across gaps or or use the sprint shout. Personally, I had no problems with Ustengrav that I can recall.

Use the sprint shout to get from column to column wherebthebridge has collapsed. There's no other way there.
Don't worry if you have to give it a miss... there's only minor loot to be had. I got some gold (not much), a couple of gems and minor soul gems. Nothing special.