1999, the headquarters of the Federal Chancellery were moved from Bonn to Berlin under the Berlin-Bonn Act, first into the Staatsratsgebäude, then in 2001 to the new building on the Spreebogen; since 2001 the secondary seat of the Federal Chancellery has been the Palais Schaumburg. A separate building, the Kanzlerbungalow served as private residence of the Chancellor and his family 1964–1999. Headquarters Bundeskanzleramt is also the name of the building in Berlin that houses the personal offices of the chancellor and the Chancellery staff. Palais Schaumburg in Bonn is the secondary official seat of the German Federal Chancellery. Opened in the spring of 2001, the current Chancellery building 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 Occupying 12,000 square meters (129,166 square feet), it is also the largest government headquarters building in the world. By comparison, the new Chancellery building is ten times the size of the White House. Because of its distinctive but controversial architecture, journalists, tourist guides and some locals refer to the buildings as Kohllosseum (as a mix of Colosseum and former chancellor Helmut Kohl under whom it was built), Bundeswaschmaschine (federal laundry machine, because of the round-shaped windows and its cubic form), or Elefantenklo (elephant loo). Access for the general public is only possible on particular days during the year. Since 1999, the German government has welcomed the general public for one weekend per year to visit its buildings – usually in August. Heads of the Chancellery Heads of the German Chancellery (Chef des Bundeskanzleramts, ChefBK) attend Cabinet meetings. They may also sit as members of the Cabinet if they are also given the position of Minister for Special Affairs (Minister für besondere Aufgaben). They are often called "Kanzleramtsminister" (chancellery minister). Otherwise, they have the rank of a secretary of state (comparable to a minor or vice minister in other countries). The current Head of the Chancellery is Wolfgang Schmidt. Typically a ChefBK is a very close advisor of the chancellor, being the primary contact to the cabinet ministers. Many of them became cabinet ministers (with other portfolios) themselves, several ministers of the interior. Frank Walter Steinmeier who served as minister of the chancery under Schröder (1999-2005) later served as minister of foreign affairs (2005-2009 and 2013–2017) candidate for chancellor (2009) leader of the opposition (2009-2013) and