escalator escalators floor levels moving stairs step steps storey transport Copenhagen Denmark HDR metro Nyberg stair staircase stairway station subway tube architecture downward empty metal movement progress solution transportation upward down inside interior move architecture styles busy decorated decoration decorative floors gallery level mall pattern patterns people shape shapes shop shopping story stylish upwards abstract angled angles architectural height high multi-level shopping-center shopping-centre storeys travel colourful interiors lights modern pastel berlin