The Atomium is a building in Brussels originally constructed for Expo 58, the 1958 Brussels World’s Fair. Designed by the engineer André Waterkeyn and architects André and Jean Polak, it stands 102 m (335 ft) tall. Its nine 18 m (60 ft) diameter stainless steel clad spheres are connected so that the whole forms the shape of a unit cell of an iron crystal magnified 165 billion times. It is now a museum.