| Answer | Crossword Clue |
|---|---|
| undergrounds | UNDERGROUND, a subterranean space or channel |
| underground | a subterranean space or channel |
| subterranean | underground / a person who or thing that is subterranean |
| microtunnelling | a technique used in laying underground pipes, etc, in which miniature boring machines excavate the required channel without breaking or damaging the road surface |
| qanats | (in the Middle East) A gently sloping underground channel or tunnel constructed to lead water from the interior of a hill to a village below |
| qanat | (in the Middle East) A gently sloping underground channel or tunnel constructed to lead water from the interior of a hill to a village below |
