cavernous
adj.adj. extremely large and deep, like a cave. You use this to describe spaces that feel much bigger than you expected.
adj. extremely large, deep, or hollow in appearance. Often used to describe architectural spaces, natural formations, or even internal body cavities.
The old cathedral has a cavernous main hall.
The explorers were amazed by the cavernous chambers deep within the limestone mountain.
The library's cavernous reading room was designed to accommodate hundreds of scholars, though its sheer scale often made the atmosphere feel slightly intimidating to first-time visitors.
Late Middle English cavernous, cavernose, borrowing from Old French caverneux or Latin cavernōsus (“full of hollows or cavities”), from caverna (“a hollow, cavity, cave”) + -ōsus (“-ous, -ose”, adjectival suffix); equivalent to cavern + -ous.