architecture construction corkscrew stairs flight of winding stairs grate grated helical metal shape shapes spiral spiral staircase stair staircase stairs wentletrap winding stairs bench climb concrete hill mountain park pavement walk step metalwork monotone old past rusty spriral staircase emergency exit escape route escape way fire exit security spiral stair artist home house elegant gold red red carpet stairway upstairs banisters blue outdoor sky steel steps barrier city London structure urban