architecture construction corkscrew stairs flight of winding stairs grate grated helical metal shape shapes spiral spiral staircase stair staircase stairs wentletrap winding stairs adlershof berlin fire exit germany reflection reflections security emergency exit escape route escape way spiral stair abstract air aluminum backdrop background blank board cg computer copyspace decorative design digital frame generated gray grid hard hole industrial industry iron layout macro mesh metallic modern net panel pattern plaque plate repetition round sheet shine sleek steel tablet template texture tile wall detail drain drainage drive driveway grey grill grille gutter lattice lined lines parallel pavement paving paving-bricks perspective soak-well solid strong urban waste architectural clean color colored colors colour coloured colours down floor floor-drain flooring marble marbling sanitation shower shower-recess tiled tiles asphalt circle cover dirty flood green grunge grungy heavy lid maintenance manhole old pipe rain rough rust rusty sewage sewer sidewalk sink stone storm street water wet