expression, noun
Refers to the open vertical space around a staircase, often in a building with an atrium-like design.
このビルは階段の吹き抜けが明るくて気持ちがいい。
This building has a bright, pleasant stairwell.
Compound of 階段 (stairs) + の (possessive particle) + 吹き抜け (open shaft, atrium).