Apart from their academic interest, studies of surfaces are a rapidly evolving domain of research because surfaces are involved in many different processes like adsorption, catalysis or thin films, where the dynamics is strongly influenced by surface structure and roughness. Even for perfect crystals, the surface is never ideal and displays steps, kinks, islands etc, and it has been shown that adsorption of an atom may be enhanced at places, like steps, where more neighbour atoms participate. Presently, observation and mapping of atomic-scale structures at surfaces rely on Scanning Probe Microscopies. Using these techniques it could be shown that annealing a crystal at a sufficiently high temperature can give rise to a "reconstruction" of the surface. Then the surface progressively approaches the ideal staircase of monoatomic steps called a "vicinal surface", with a terrace length given by where is the step height and the cut angle. If the cut angle is small enough the terrace length can be larger than the wavelength of light : then the vicinal surface is expected to give rise to coherent diffraction of a laser beam. We show, with a 1mW Helium-Neon laser, that the diffracted beams, although they are very weak, are indeed observable in a reasonably clean environment and provided that efficient beam dumps completely absorb stray beams associated with specular reflection at the sample surface. Both visual observation or photographic recording are adequate to visualise the diffraction pattern. This method allows instantaneous determination of the direction of the steps, normal to the direction of the diffracted beam, as well as the terrace length, through the diffraction angle. Furthermore the divergence characteristics of the diffracted beam gives information about the variation of the terrace length and direction over the laser spot size. One can then scan a 10mm x 10mm sample in the time required to record the AFM scan of a 10µm x 10µm surface. This illustrates the advantage, when scanning large surfaces, of the "parallel" character of an optical method which uses diffraction. Photographic recordings of laser beams diffracted from annealed sapphire and silicon samples will be presented. (*) Laboratoire de l'Ecole Normale Supérieure et de l'université Pierre et Marie Curie, associé au CNRS (UMR 8552)