i like this article from designtaxi…

London-based art and design studio Troika has constructed an archway with just rays of bent light. As part of the Biennale Interieur 2012 in Kortrijk, Belgium, this light installation is entitled ‘Arcades Project’ and seeks to explore the boundaries between intangible and physical space. The archway is created by passing columns of light through a Fresnel lens, which not only refracts the light rays but bends them hyperbolically to form the curved shape of the arches. Reminiscent of gothic architecture, the lights create a sense of structure where there is none.

thanks ian for pointing me here