Were there any prisons in ancient Greece?

Answer 1

Prisons as we understand them - as a place of reform - are a modern invention. Before the 19th Century idea of a penitentiary, prisons were places of detention where people were held until they were punished - execution, flagellation, sale as slaves, etc, or released sometimes if found not guilty.

So yes, there were prisons cells, but not penitentiaries.