noun
underground space; subterranean space
Refers to any space or cavity located below the ground surface, including natural caves, tunnels, basements, or underground facilities.
この都市には広大な地下空間が広がっている。
A vast underground space extends beneath this city.
地下空間の有効活用が都市計画の課題だ。
Effective use of underground space is a challenge for urban planning.
Compound of 地下 (underground) and 空間 (space). The kanji components are straightforward: 地 (earth), 下 (below), 空 (sky/empty), 間 (interval/space).