abstract angles appearance backdrop background backgrounds barrier blocks coloring colors colouring colours constructed fitted large limestone linear lines mortar perspective perspectives rock rock-face rockface rough secure security solid stone stones stonework strength strong surface surfaces texture textures variations variety wall walled well-built colored coloured contours contrast contrasts cracks fissures flaws layered layers levels light natural rocky rugged sandy shade shadows shape shaped shapes strata stratum sunlight sunny sunshine textured veins wallpaper brown ribbons shades of color shades of colour