Only one per stronghold, and it is never within 5 rooms of the starting staircase. In most cases, this room cannot be overwritten by other structures generated around it.
There are two pools of 3 lava sources in the front sides of the room and a bigger lava pool of 9 below the end portal, and 16 windows of 2 iron bars in the room, with the entrance, always being a gate.
Each room has an entrance, which is either a plain 3×3 opening, a wall with a wooden door, a wall with an iron door (with buttons), or a 3×3 opening with a gate of iron bars along the top and sides. Strongholds feature various types of main rooms.
In generated chest corridors and storerooms, dispersed chests containing a variety of loot can be found. Stairs that generate within these structures include stone brick and cobblestone stairs, but not their mossy variants. Strongholds are lit by enough torches to provide visibility in most areas, though not enough to suppress mob spawns.
Infested cracked stone bricks and infested mossy stone bricks do not generate, unless silverfish enter these blocks. They contain several doors and rooms made mostly of stone bricks (45%), mossy stone bricks (30%), cracked stone bricks (20%) and infested stone bricks (5%).