This is an illusion due to the fact that your cathedral model is very big and placed far away from the viewpoint. You need to scale down your cathedral model and center it around the avatar. For example, try initializing the cathedral with the following values:
Code:
room = viz.add('cathedral.WRL')
room.scale([0.01]*3)
room.rotate(180,0,0)
room.appearance(viz.MODULATE)