This phrase is a wonderful ancient Greek proverb. It is said that an abundance of owls famously roosted in the rafters of the original Parthenon.
This means, something that is pointless / a useless or futile act / something which is highly uneconomical / something superfluous.
Take coal to New Castle also convey the same meaning.
Example
There is not point in buying gifts for her wealthy friends, ‘It’s like bringing owls to Athens
The minister has a plan to increase taxes, thinking that this would improve the economy. It would bring owls to Athens