Sketch representing the large-scale density field and its topology using mountains as an analogy. The black lines following the ridges of the field represent the cosmic filaments. The red and green circles show, respectively, the positions of the CPmax, or peaks, and the (filament-type) saddles of the field. These are the endpoints of filaments within the DisPerSE framework. The blue circles locate the wall-type saddles of the field. Minimum density critical points are not represented.