A square architectural interior visualization of a refined modern duplex staircase. Warm white plaster walls, floating natural oak treads, slim matte-black metal railing, a double-height void, soft daylight from a tall side window, subtle concealed LED lighting beneath the handrail, pale limestone floor, one sculptural indoor plant, realistic residential proportions, uncluttered editorial composition, no people, no readable text, no logos, no watermark.