A luminaire comprising a transparent light guiding structure (2), including a stack of transparent, flat panel light guides (3). Each panel light guide has an in-coupling edge (4) adapted to receive light from said light source and couple this light into the light guide, and at least one out-coupling surface (10, 10a) adapted to couple light out of the light guide, wherein the out-coupling surfaces being distributed along a plane of extension of said light guiding structure. The stacked light guiding structure according to the present invention is easy to manufacture even for large sizes, and consists principally of existing elements (flat panel light guides). Also, an improved transparency can be achieved with this design.