abstract angle angles appearance architectural architecture background basic brick brick-wall bricks color colored colors colour coloured colours exterior external perspective perspectives rough smooth solid standard strength surface surfaces texture textured textures uneven variation varied various wall wallpaper building cement concrete detail rugged stone irregular old stones structure backdrop barrier bolders boulders cemented coated constructed cover covered erosion-prevention fitted hill mortar random randomly-coursed Rendered retaining-rocks retaining-wall rock rocks rocky secure security slope sloping stone-walled stonework strong variations variety walled well-built paint raw street crack rot time wood