The Prison is a large complex of several white buildings, surrounded by walls. It is located east of the center of the map. Three of the prison blocks, as of the new update, are enterable. As the entrance has military tents and barricades set up, one can presume that the Military used this area to evacuate and shelter Civilians. Given how there are no Prisoner Infected, but there are Police Infected, one can presume that the Police gathered whatever weapons they could find and either killed all the prisoners, or they were overrun and and the Prisoners experienced the slow, painful death of starving in their own cells. Inside the prison blocks are a few useful items, including food and drinks, civilian ammo and utilities. It has one large entrance and one large broken wall entrance, and can be barricaded if you have enough time and materials. There are a few buildings which can not be entered, but most of these do however have ladders to the rooftops. Prison is also a place where fresh spawns look for weapons and supplies, so it can be quite dangerous to go alone.
There are small guard towers more or less evenly spaced around the walls, and two larger towers near the main entrance. Military grade weapons , utilities and backpacks , and occasionally attachments spawn inside the guard tower's. The walls have many holes, so barricading the whole complex is not an option for most survivors. Outside the main building is a courtyard, which has a few loot spawns and barricades and there is a military tent and a few vehicle barricades outside the main entrance. Cars can also spawn at the barricades.
The prison, as seen from a nearby hill.
A band of bandits at the prison.
A small bandit group of three members in the prison.