The Hilltop House was originally designed by architect Thornton Ladd in 1953 and was reworked by Marmol Radziner.
From the site:
Located in Pasadena, California, the Hilltop House and Studio were originally designed by architect Thornton Ladd in 1953. Spread over five acres, the mountaintop retreat is comprised of a 6,700 square foot house and a 1,300 square foot detached studio. The resident of the studio converted the space into a modern guest house. Laddâ€™s original design integrated indoor and outdoor spaces and took advantage of the dramatic views. The ownerâ€™s interest in Japanese architecture and design informed the choice of interior materials – warm woods including cedar and maple for the floors and ceilings, furnished with tatami mats.