The South transept is filled with the large pipe organ, but the oculus (the Dean’s window) is still clearly visible from the crossing. The design of the outer painted decoration matches the design on the ends of the organ pipes. An oculus (Latin for 'eye') is a circular opening in the centre of a dome or in a wall. Originating in antiquity, it is a feature of Byzantine and Neoclassical architecture. This oculus is predominantly clear glass, but with distinct traces of colour in its patterning. There are problems with definition here: oculus or rose window?!