The tower features a triangulated 'diagrid' design, which is a highly efficient solution that utilizes 20% less steel than a conventionally framed construction. It provides a striking facetted silhouette on the Manhattan skyline with the corners trimmed back between the diagonals. This allows more floor space to be made available from each floor area. The Hearst Building was one of the first skyscrapers to utilize reinforced concrete as its primary structural material. This enabled the architects to create a thinner shell structure for the building, which reduced its weight and cost while at the same time providing greater strength. Another unique feature of this building is its use of art as exterior decoration. The upper floors of the tower were designed by renowned architect Louis Kamper who also created the decorative art deco lobby inside the Hearst Tower today. The lower floors were designed by Henry Cobb and built by the Associated Construction Company. They used colorful ceramic tiles as their main form of decorating the exterior of the building. The Hearst Tower was completed in 1971. At the time it was the tallest all-concrete building in the world. It still holds this title today. The tower has 72 stories plus a penthouse apartment. It is 605 feet tall with a diameter of 90 feet. The Hearst Building has been listed on the National Register of Historic Places since 2003.