The first section of the central vertical mast was put in place beginning of 1957. It was a tube 59 ft long, 10.8 ft in diameter and weighed 39 tons. (The structure of this tube was gone into previously). The ring where the twelve arches of the base sphere are articulated, is welded on the top part.

The second operation carried out consisted in placing the twelve rectangular section columns supporting the large 33 ft diameter crown, which carries the lower ends of the 12 box spars making up the main framework of the base sphere. The beams for the two floors, and the base sphere. The beams for the two floors, and the secondary framework linking the large arches, were laid in March 1957; the skinning with polished aluminium panels followed immediately - as it was necessary to test the new spherical triangles system - and the base sphere was finished in early May. In the meantime, erection of the central mast was carried on with an inclinable spar 59 ft high which the riggers elevated and fixed on the central mast as it grew higher. The central mast, which serves as the lift cage, was thus built up to a height of 335 ft, stabilised by wire struts; it served as a main erecting mast after the three bipods and the framework of the three lower spheres had been put in place.

The bipods were raised into their two spherical knee-pans by suspending them above their centre of gravity between two rigging booms 130 ft high. The bipod was provisionally steadied by an inclined mast while the framework of the lower sphere and the 95 ft tube connecting it to the base sphere were being put in place. The first bipod was set up on 15th June; the third on 25 September 1957. The central sphere was erected in October.

In October, November and December 1957, the framework of the three lower spheres was set up with the help of hoisting booms installed on the lower floor level of the sphere. The framework of the top shere was assembled during December 1957 and January 1958. For this particular assembly operation, the riggers had replaced the arm that surmounted the central tube by a pyramid and a 49 ft spar boom. This rigging set, which was heavily trussed and with a base 340 ft above ground, stayed in place till the end of the erection of the Atomium, i.e. end March 1958.

After that, a large 148 ft long crane boom was installed on a platform immediately above the central sphere. It enabled the assembly of the three higher spheres and the 12 tubes of approximately 30 tons each which connect them with the other spheres.

The assembly of the three middle spheres presented quite a problem in view of their height (246 ft at the equator of the sphere) and their distance from the central mast.

It was solved by erecting three temporary 213 ft high masts, which supported the cube that formed the center of each middle sphere. The cube, with 13 ft sides, is made with welded plates. It is disposed as the Atomium itself, i.e. with a vertical diagonal. Four liaison tubes connect upto this cube, which is hollow and allows passage for the stairs coming from the top sphere.

The middle spheres are also made up of 12 arches which are attached top and bottom to two small towers fixed into the upper and lower central cube of the sphere.

Assembly of the middle spheres began in January 1958, to end on 25th March by the simultaneous removal of the three temporary 213 ft supporting masts.

The erection of the Atomium went through some extremly spectacular phases and the "Ateliers de Construction de Jambes-Namur" can be whole-heartedly thanked for the wonderful job done, whether by the design office, which conceived the principles and lifting equipment, or the teams of riggers, which really surpas- sed themselves as far as efficiency and will to solve all difficulties were concerned.