Well, whadyaknow, there's a topic just for the issue I mentioned in passing in the previous topic I posted in. Yes, this is a secret. There are a scroll and coins inside if memory serves, but the reason it doesn't open in 1.0 is because there's also a light fixture big enough to block part of the pillar, and so the engine refuses to open it. I'm assuming this didn't get fixed in 1.04 and needs to be on the TODO list - moving the light fixture may be enough to get it working. It's very much off-center in 1.0.
I'm surprised so many of these details didn't get a canonical reply as to what's happening and why...