Nether Fortress



Nether Fortresses, first introduced in the 1.9 Pre-Release, are structures that are generated in the Nether. They include bridge structures constructed of Nether Bricks, Nether Brick Fences, and Nether Brick Stairs. They often contain Blaze spawners, and are the only place that Nether Warts can be naturally found. A common misconception is that Magma Cubes spawn more frequently in Nether Fortresses. The reverse is actually true, because the confines of the structure and the lack of large flat surfaces reduces the chances of a Magma Cube to spawn.

Structure
Nether Fortresses are very large complexes made mainly of Nether Bricks. Nether Fortresses can often tunnel through Netherrack, and the inside of the tunnels will be cleared of Netherrack by the terrain generator. However, at broken bridge sections, the terrain is not cleared, creating a tunnel that leads straight into a flat wall of Netherrack. Their main structure takes a shape of bridges with supporting pillars outside and corridors inside, both which have 3-blocks wide walking space. The bridges can be broken at the end. The interior of the structures have 1x3 windows with Nether Brick Fences as the windowpanes. The fences also form gate-like structures at the entrances of some rooms and corridors. The rooms include:
 * Lava well rooms
 * Rooms with Nether Brick Stairs in the center and Soul Sand at sides of the stairway with Nether Wart growing on it.
 * Rooms with Blaze spawners. Nether Brick Stairs can lead up to them. The rooms have Nether Brick Fences.

Trivia

 * Because Nether Fortresses are built out of Nether Brick that cannot be destroyed by anything short of a TNT blast, consists of 3 block wide tunnels, which prevent the 4 block wide spawning requirements, and have windows built out of the semi-transparent Nether Brick Fences, they can be a safe haven from Ghasts.
 * Nether Fortresses will still be generated even if the "Generated Structures" option is turned off. This is most likely because they are required to find Blazes, and collect all the achievements.