EnquireThis is a relatively well known sculpture in Middlesbrough town centre. A quick search on flickr turned up around 200 photographs of it, less than 5% of which are of the inside of the sculprure like this one. Mostly what you see are fairly pedestrian 'documentary' type shots of the sculpture. But I am always wary of simply photographing somebody else's work - be that graffiti, sculpture or architecture - the photograph must bring something new to the party.
So one of my 'rules of thumb' is to look for an angle that most people (95%?) won't have seen; make use of the camera to show the unseen. Or even the unseeable.