I was playing through Dragon Age today when I saw an X on my map. I hovered over it and it said "secret room". I was in the raw fade so since I had my different forms, I assumed there was a secret room (not knowing I was in the secret room), so I changed my form into a rat (while hugging the pillar) and surprisingly I ended up on top of the pillar! I moved forward a little and fell off the map! Here are some screen shots showing the process.
This is the area:

This is the pillar:

Me on top of the pillar after transforming:

I then proceeded backwards and off of the map. Some screens outside of the map:



Was a lot of fun

If anyone else has posted this already, I apologize, but I promise you I found this out 100% by myself accidentally.