"In civil engineering a shaft is an underground vertical or inclined passageway. Shafts are often entered through a manhole and closed by a manhole cover. They are constructed for a number of reasons including:
For the construction of a tunnel
For ventilation of a tunnel or underground structure
As a drop shaft for a sewerage or water tunnel
For access to a tunnel or underground structure, also as an escape route" - (en.wikipedia.org 08.08.2021)
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