The Atomium ( /əˈtoʊmiːəm/ ə-TOH-mee-əm) 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.

Tubes of 3 m (10 ft) diameter connect the spheres along the 12 edges of the cube and all eight vertices to the centre. They enclose stairs, escalators and a lift (in the central, vertical tube) to allow access to the five habitable spheres which contain exhibit halls and other public spaces. The top sphere includes a restaurant which has a panoramic view of Brussels. In 2013 CNN named it Europe's most bizarre building.