Matter density distribution in two regions with a side length of 117 $h_{100}^{-1}$ Mpc from the Millennium simulation. The depth of the slices through the simulation is 15.6 $h_{100}^{-1}$ Mpc. The matter density is colour-coded, with increasing density in rainbow colours from blue to red. The positions of the clusters, selected analogously to the clusters of the extended CLASSIX survey, are marked by black dots.