A barn was a storehouse or granary for grain. In the East, grain was commonly preserved in a dry underground pit or cistern, though buildings could also serve as barns or storehouses.
Jesus used barns in teaching about stored crops and God’s care for the birds. The barn or storehouse could also serve figuratively for heaven in the supplied material.
Grain was stored after threshing and winnowing. Carefully prepared pits or caves protected it for years and helped conceal it from robbers and tax-gatherers. In Roman times, a storehouse could also be a building.