Update #3
Yes, it’s the dome once again. Apparently I just can’t stop working on this scene. Originally it was meant to be used in the Unreal 2004 engine, but it’s looking a little out of date recently. Basically all the models got revamped into a more coherent and smooth style and the arches are a little more dynamic and structurally sound. Since I basically changed the models and added in a few things, the textures need to be redone for the most part. I found some awesome reference images from the Saadian Tombs and it should be done within the week.
In the meantime, marshmallow dome:

