Staircase, Wood Tread, and Metal Railing Tehrani designed the millwork throughout, collaboratingwith fabricator C. W. Keller + Associates. Seen from the foot of the central staircase, a set of blue, gray, and yellow Alphabet sofas by Piero Lissoni for Fritz Hansen furnish the family room on the first floor; the dining area lies just beyond, adjacent to the kitchen. A small aperture provides a peek into the second stairwell, which is situated at the center of the floor plan and leads to the garden level.  Photo 7 of 15 in What’s the Twist Behind This Home’s Sinuous Staircase? Ordinary Plywood