along which light from projector 30 passes to screen 28 preferably is such that an equal angle of reflection is along the centre line of chamber 18 projector 30 preferably has a lens which compensates for the increasing projection distance toward the bottom of screen 28 viewers are able to pass into and from lobby 16 via doorways 16 39 16 34 and across the adjacent end of chamber 18 at a selected level of gallery 20 locking along chamber 18 viewers can observe a primary image projected on screen 28 from projector 30 as well as a plurality of secondary images produced by multiple reflections of the primary image produced by tiles 26 due to random slight variations in the reflective orientation of adjacent tiles 26 the secondary images appear to be build up from a mosaic of picture elements such as shown at 32 in fig5 screen 28 can be a white or silvered screen such as of conventional form and in such case it will not be of such mosaic form and discernable as differing from the secondary images however if required the surface of screen 28 also can be provided with an array of similar tiles so as to minimise perceivable differences between the primary image and the secondary images fig4 shows a typical multi image cluster formation of the primary and secondary images.