The Bohrok nests were the dwelling place of the Bohrok swarms. Bohrok nests extended from below the surface of Mata Nui to below the city of Metru Nui. Each contained hundreds of Bohrok and Bohrok Va.
An entrance to the Bohrok nests was located in the area of cold, rocky plains lying between Ko-Wahi and Le-Wahi, situated in a flat, low-lying area littered with enormous boulders. Hidden in the center of a ring of huge boulders was an enormous, yawning chasm in the ground. It plunged straight down into the earth, neither narrowing nor sloping before disappearing into the darkness below. All around the walls, Bohrok and Bohrok Va clambered up along steep channels carved in the stone. An entrance was burned straight through one of the boulders surrounding the top, big enough for several Bohrok to pass through side by side.
The steep, rocky walls of the nest entrance led down into the darkness into a large, smooth tunnel leading deep into the earth. Pohatu, an expert in stone, noticed that the walls were too smooth to have been dug by Matoran or Bohrok, which worried him.[3, 2]
The smooth tunnel led to an opening in the floor, which led to the heart of the Bohrok nest itself. Beyond this opening was a small chamber lit by a greenish glow. Beneath the floor of this chamber was another chamber. This chamber was massive, dimly lit, and round. Its floor was smooth, except for deep niches carved into it, whose shapes matched the krana. When the Toa placed the krana they collected into these slots, the chamber shook, and its walls fell away, revealing six enormous metal doors. These doors opened up to six identical tunnels shrouded in smoke and darkness. In each of these was found an Exo-Toa.
After the Toa's fight with the Bahrag, an avalanche completely covered the entrance to the Bohrok nest in Po-Wahi with huge rocks. The cave entrance was completely filled in with rocks. The entrance was located at the top of the slope of a hill, although it was not visible from the base of the hill.
Bohrok nests were all over the place on Mata Nui.
There were Bohrok nests underneath Metru Nui as well because there wasn't enough room for all of them to fit above Metru Nui's dome.
The Bahrag nest was probably located at a higher depth than Mangaia and Metru Nui.