A grouping of clusters of galaxies. Many superclusters are known, containing anything from around 10 to more than 50 rich clusters. The most prominent known supercluster is the Shapley Concentration, about 450 million l.y. away in the region of Centaurus, while the nearest is the local supercluster. Superclustering is known to exist on scales up to 300 million l.y., and possibly more. See also large-scale structure.