The Bundeskanzleramt or the German Federal Chancellery is a federal agency serving the executive office of the Chancellor, the head of the German federal government. The Bundeskanzleramt primary function is to support the Chancellor in leading the activities of the federal government. The chief of the Bundeskanzleramt occupy the position of either a Secretary of State (Staatssekretär) or a Federal Minister (Bundesminister). Federal Chancellor Otto von Bismarck first established a Bundeskanzleramt as his office. During the German Empire in 1871, the Bundeskanzleramt was renamed to Reichskanzleramt.The current Chancellery building, opened in the spring of 2001, was designed by Charlotte Frank and Axel Schultes and was built by a joint venture of Royal BAM Group's subsidiary Wayss & Freytag and the Spanish Acciona from concrete and glass in an essentially postmodern style. The Bundeskanzleramt Occupies 12,000 square meters, it is also the largest government headquarters building in the world.