An illumination system for indirectly or directly illuminating an outer edge arrangement of a structure covered in tiles, such as for example a step of a staircase, includes at least one elongate profile that forms a base arm, a decorative arm projecting from a free end of the base arm and the outer surface of which forms a visible decorative surface in the correctly arranged state, and a fastening arm projecting from the other free end of the base arm, arranged opposite the decorative arm, at least one illuminant that is fastened or can be fastened within the receiving space defined by the base arm, the decorative arm and the fastening arm, and at least one elongate diffusion disc cover that can be fixed to the profile.