"Dark matter gravitationally attracts baryonic matter, and it is this normal matter that astronomers see forming long, thin walls of super-galactic clusters. ... The Great Wall is a massive array of astronomical objects named after the observations which revealed them, the Sloan Digital Sky Survey.  An eight year project scanned over a quarter of the sky to generate full 3-D maps of almost a million galaxies.  Analysis of these images revealed a huge panel of galaxies 1.37 billion light years long, ...
... Sloane_9:  This isn't the only wall out there -- others exist, all with far greater lengths than width or depth, actual sheets of galaxies forming some of the most impressive anythings there are.  And these walls are only a special class of galactic filaments, long strings of matter stretched between mind-breaking expanses of emptiness. ... Some of these elongated super clusters have formed a series of walls, one after another, spaced from 500 million to 800 million light years apart, such that in one direction alone, 13 Great Walls have formed with the inner and outer walls separated by less than seven billion light years. ... Recently, cosmologists have estimated that some of these galactic walls may have taken from 80 billion to 100 billion, to 150 billion years to form in a direct challenge to current age estimates of the age of the Universe following the Big Bang."

http://www.dailygalaxy.com/my_weblog/2011/03/do-the-great-walls-the-largest-structures-in-the-universe-contradict-big-bang-theory.html