LAVAUX-SAINTE-ANNE, BELGIUM — A 60-meter tall semi-circle of steel cast to look from a distance like a towering but incomplete ring, is set to surprise drivers taking a scenic tour in the south of Belgium to France or Luxembourg. Designed by French conceptual artist Bernar Venet and called L’Arc Majeur, the huge sculpture was installed recently at Lavaux-Sainte-Anne, a small town along the busy 411 highway. “Today we are installing, what everybody agrees to say, the biggest sculpture in the world,” said Mr. Venet, who called the project the realization of a 35-year dream. Mr. Venet initially wanted to install the sculpture, made from 200 tonnes of steel and set in 2,800 tonnes of concrete, in France but ran into various obstacles and eventually found a home for it in Belgium. “Two hundred meetings with French, and it didn’t work for so many years. One week of talks in Belgium, and it’s done,” said Mr. Venet, who was awarded the International Sculpture Center’s Lifetime Achievement in Contemporary Sculpture Award in 2016.