Egypt has inaugurated a new armed forces headquarters, which observers say is the largest in the world, with an elaborate ceremony and a rare appearance from the president and former general Abdel-Fattah el-Sisi in military uniform.The Octagon, as the complex is being called, consists of eight buildings each with an eight-sided floor plan in an area of around 90 sq km (34.7 square miles), the size of the Portuguese capital Lisbon.It has replaced the Pentagon, the headquarters of the US Defence...