The 1976 National Air and Space Museum, designed by Gyo Obata of the St. Louis-based firm, Hellmuth, Obata and Kassabaum (HOK) encompasses the achievements, the zeitgeist and the perpetual movement of midcentury aviation and space. Constructed of four, monolithic block structures clad in pink Tennessee marble, Obata was influenced by the design of aircraft hangers and the stark utilitarianism of aviation architecture. The structure anchors a portion of the national mall which lies at the foot of the US Capitol. Ongoing preservation efforts concern a postmodern addition on the East end of the building, also designed by Obata in the early 1980s. The addition is set to be demolished as part of the Bezos Learning Center.