The Atomium is a monument in Brussels, originally built for Expo '58, the 1958 Brussels World's Fair. Designed by André Waterkeyn, it stands 102 metres (335 ft) tall. It has nine steel spheres connected so that the whole forms the shape of a unit cell of an iron crystal magnified 165 billion times. Tubes connect the spheres along the 12 edges of the cube and all eight vertices to the centre. They enclose escalators connecting the spheres containing exhibit halls and other public spaces.