Minecraft Wiki
This page documents the layer-by-layer composition of a given generated structure or terrain feature. 

Each of the jails have a Vindicator spawn in front of the doors.

Large Jail Room (2x2_a1)

The two cobblestone stairs are upside down and face each other.

Medium Jail Room (1x2_b1)

The Medium Jail is also known as the Redstone Jail.

All of the cobblestone stairs are upside down.

Small Jail Room (1x2_b2)

The oak wood stairs on Layer 1 past row 10 are upside down.
The cobblestone stairs on Layer 4 are upside down and face inside.