Wolfgang Buttress had a vision of a sculpture representing a rising sun over Belfast. A tight budget, and a grand ambition, required a solution where the artistic piece was a pure engineering object that used the minimum amount of material to its maximum efficiency. The solution was two hovering concentric geodesic spheres made from 60mm diameter steel tubes.

The outer 30m diameter sphere is held aloft with 21 carefully positioned slender steel columns. These columns are inclined so that they brace the sphere laterally and support its weight by meeting it at an exact tangent to the surface. The inner 15m sphere is held by a network of cables that create a three-dimensional tensegrity within the outer structure, making it appear to float. All together there are 2,421 tubes and 804 bolted joints.

The inner sphere was built stick by stick. The outer sphere was made from prefabricated ëpetalsí assembled on a system of temporary works to hold their shape and hold them in position. Before the five petals forming the cap of the sphere were installed, the inner sphere was lifted into the middle of the outer sphere. Finally, with the construction complete, gravity could be turned on and the temporary works removed.

Completed 2011.

Project Information


Belfast City Council


Wolfgang Buttress




Michael Walsh


Structural Award, Small Projects category 2011