井道
井道
井底水仓
井底水仓
垂直大炮眼
楼梯井

Wellhole \Well"hole`\, n.
1. (Arch.)
(a) The open space in a floor, to accommodate a staircase.
(b) The open space left beyond the ends of the steps of a
staircase.

2. A cavity which receives a counterbalancing weight in
certain mechanical contrivances, and is adapted also for
other purposes. --W. M. Buchanan.