in most prisons, the is an important social place where people talk, groups congregate, and the social business of the prisons is conducted.

The correct answer is the yard.
You must have seen in many movies that inmates spend a lot of time in the prison yard, usually playing some sports, such as basketball. It is an important place for prisoners because they get an opportunity to socialize and to wind down a bit, and where they can relax and talk. 

Who it was like back then