Designed by the Belgian engineer Andre Waterkeyn for the 1958 World's Fair in Brussels, the Atomium is a massive structure shaped like an iron crystal. It served as the fair's main pavilion and symbolized an optimistic faith in a peaceful modern age powered by scientific progress. Though originally intended to be removed after the fair, its popularity induced the Belgians to leave it standing. Five of its nine spheres are currently open to the public. The highest one is a restaurant, rest contain a variety of exhibitions. Visitors travel between spheres via the connecting tubes using stairs, escalators, or (in the central tube) and elevator.