Spheres are placed at the vertices and center of a cube, which is aligned vertically with one of its body diagonals. The spheres are connected with cylinders. This is the basic arrangement of the Atomium, a monument built for Expo '58, the 1958 Brussels World's Fair. It is 102 meters (335 feet) tall. This can also be regarded as a model unit cell of a body-centered cubic (BCC) crystal system.