Places below the main part of a building, usually used for storage.
Subcellars are usually dark and cool, and they are good places to keep things safe.
Examples:
The subcellars are where we keep all the old things.
We found some old books in the subcellars.
She went down to the subcellars to get some potatoes.
The subcellars are so dark, I'm a little scared!
The subcellars are like a secret underground world.
In the subcellars, we found a treasure map.