Jack and Isabel Bain from Brisbane, Queensland, Australia did a ten month round the world post retirement trip in 1966. The Atomium (/əˈtoʊmiːəm/ ə-TOH-mee-əm, French: [atɔmjɔm], Dutch: [aːˈtoːmijəm]) is a landmark modernist building in Brussels, Belgium, originally constructed as the centrepiece of the 1958 Brussels World's Fair (Expo 58). Designed by the engineer André Waterkeyn and the architects André and Jean Polak as a tribute to scientific progress, as well as to symbolise Belgian engineering skills at the time, it is located on the Heysel/Heizel Plateau in Laeken (northern part of the City of Brussels), where the exhibition took place. It is the city's most popular tourist attraction, and serves as a museum, an art centre and a cultural destination. The Atomium stands 102 metres (335 ft) tall, making it one of the tallest structures in Belgium. Its nine 18-metre-diameter (59 ft) stainless steel clad spheres are connected in the shape of a unit cell that could represent an iron crystal magnified 165 billion times.[5] Steel tubes connecting the spheres enclose stairs, escalators and an elevator (in the central, vertical tube) to allow access to the six visitable spheres, which contain exhibit halls and other public spaces. The top sphere includes a restaurant with a panoramic view of Brussels. The building was completely renovated between 2004 and 2006 by the companies Jacques Delens and BESIX. The building is located on the Square de l'Atomium/Atomiumsquare, at the intersection of the Boulevard du Centenaire/Eeuwfeestlaan with the Avenue de l'Atomium/Atomiumlaan and the Avenue de Bouchout/Boechoutlaan, and opposite the Centenary Palace of the Brussels Exhibition Centre (Brussels Expo). It is served by Heysel/Heizel metro station on line 6 of the Brussels Metro.