Leading him into the centre and highest part of the palace, Seren opened a great door and behind it Gwylym saw a massive round crystal that was as large as a two storey dwelling. It was a perfectly shaped round orb that seemed to be bursting with colour and internal movement. Gwylym realised he had to be looking at the Great Crystal Ball. Its contents were not only moving around, but it looked like there was another world living inside it!
Ref: DDD Missed Once Look Twice
Artist Morgan Wyche, GwynfydThinking