In the famous painting, "Death of Socrates" by Jacques Louis David (1787), the prison is pictured in grandiose fashion. It almost looks like part of an Emperor's palace! (This prison appears on the homepage of this project.)
In fact, the actual prison would have been very humble. Incarceration is a recent
form of punishment in Western civilization (i.e. in the past few hundred years). In order
of increasing magnitude, the available punishments in Socrates' day,
and for many centuries thereafter, would have been payment of fines, exile, and death.
Because imprisonment was rare and only temporary, there was no need for jails qua
institutions in ancient Greece.