A burrowing that forms a spherical "bubble" in the rock. They were formed during the excavation of tunnels around the Cavern like "nodes" between each straight-line section. They were typically fitted with an airtight gate with a thick collar, that would be sealed in case of emergency, isolating parts of the tunnel.

These borrowings are perfect hollow spheres with a platform for the excavators. The crew rested or carried on experiments while charting each next stage. Beneath the gridwork platform there is a second, smaller platform. When the Observers came to inspect the process of the Great Shaft, the quarters for the junior members of the expedition were removed there.[1]

On Aitrus's Map some tunnels are shown around the Cavern with many nodes. From D'ni to the Great Shaft there are 17 numbered nodes.


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