A roughly two-dimensional concentration of galaxies, at least 200 million by 600 million l.y. in extent, but less than 20 million l.y. thick. It contains many thousands of galaxies and has a mass of at least 10¹⁶ solar masses. The Great Wall extends more than 120° across the sky (8–16 h RA) and is about 250 million l.y. away. This and other similar features, together with the many filamentary features in the distribution of galaxies, suggests that the large-scale structure of the Universe may be cellular in nature, with other Great Walls forming the faces of the cells and filaments of galaxies forming where these faces intersect. See also redshift survey.