The Flintstone House is a free-form, single-family residence in Hillsborough, California[1] overlooking and easily seen from the Doran Memorial Bridge carrying Interstate 280 over San Mateo Creek. The house was designed by architect William Nicholson and built in 1976 as one of several experimental domed buildings using new materials. It was constructed by spraying shotcrete onto steel rebar and wire mesh frames over inflated aeronautical balloons.[5] It has approximately 2,700 sq ft (250 m2) of living space including three bedrooms, one accessed via a spiral staircase inspired by an icecream cone that at the top is the same diameter as the room, and two bathrooms, and has a two-car garage.All the interior surfaces are rounded, and the master bathroom has a floor of rocks instead of tiles.[6][5] Originally off-white in color, the house was repainted deep orange in 2000, and one of the domes was later painted purple.