CfA2 Great Wall

The Great Wall is one of the largest known super-structures in the Universe.
It is a huge group of galaxies about 200 million light-years away. The Great Wall is like a long, thin line filament: it is over 500 million light-years long, 300 million light-years wide, but only 15 million light-years thick. It was discovered in 1989 from redshift survey data.
We do not know how much farther the wall extends. Our view is blocked by the galactic plane of the Milky Way. The gas and dust from the Milky Way (known as the Zone of Avoidance) obscures the view of astronomers. This makes it impossible to find out if the wall ends or continues on further. 
In the standard model of the evolution of the universe, such structures as the Great Wall form along and follow web-like strings of dark matter. It is thought that this dark matter dictates the structure of the Universe on the grandest of scales. Dark matter gravitationally attracts baryonic matter, and it is this 'normal' matter that astronomers see forming long, thin walls of super-galactic clusters.