The Opposite Sphere, Outdoor sculpture in Notviken-Mjölkudden, Luleå, Sweden

The Opposite Sphere, known locally as Rostbollen, is a sculpture 8 metres high and 17.5 tonnes in weight, made of 200 rust-resistant steel plates. It stands in the Notviksrondellen roundabout where national road 97 enters Luleå. The plates were rolled in Borlänge, cut in Degerfors and assembled in Luleå.

The sculpture was first built in snow, four metres in diameter, and won gold at the 1992 Albertville Olympics. The permanent version in Notviksrondellen was made with Mats Eriksson of Relitor Engineering AB in rust-resistant Domex steel, at a cost of 1,000,000 kronor. Its 200 plates were rolled in Borlänge, cut in Degerfors and assembled in Luleå.

Locals call the sculpture Rostbollen, "the rust ball", after the weathering steel of its 200 plates. It stands in Notviksrondellen where national road 97 enters Luleå, and is meant to symbolise the city as a steel town. The same form was first built in snow, four metres across, and won gold at the 1992 Winter Olympics in Albertville.

The sculpture is in a public area with parking nearby and is free to visit at any time. The best time to visit is on clear days when light effects through the perforations are most visible.

The sculpture began as a four-metre snow version that won gold at the 1992 Albertville Olympics; the steel sphere in the roundabout is twice that size, eight metres in diameter. Its 200 plates were rolled in Borlänge, cut in Degerfors and assembled in Luleå, at a cost of one million kronor.