Stronghold



Strongholds are structures that occur naturally underground. They contain multiple rooms, corridors, stairs, doors and other aspects. Strongholds also contain a portal room with an unactivated End Portal, which when activated with twelve Eyes of Ender can be used to travel to The End. Strongholds can be located with an Eye of Ender.

Appearance


Strongholds vary in size. They are labyrinthine and contain several doors and rooms made mostly of Stone Brick, Mossy Stone Brick, and Cracked Stone Brick. Some treasures found in strongholds include Paper, Redstone, Books, Enchanted Books, Coal, Gold Ingots, Iron Ingots, Compasses, Apples, Golden Apples, Ender Pearls, Iron Chestplates, Iron Boots, Iron Pickaxes, Iron Helmets, Maps, Iron Swords, Obsidian, and Diamonds.

Strongholds are primarily generated underground, often unexposed to the surface and only visible within caves, possibly even underwater caves. In some seeds they may be connected to a dungeon or even merge into an abandoned mine shaft. Strongholds are vacant except for regular mobs that spawn under normal conditions. Strongholds are where Silverfish can spawn, created when someone either mines one of the blocks within, or finds the end portal room, which contains a silverfish spawner.

Rooms within the Stronghold
Strongholds feature various types of main rooms, such as Prison Cells, Libraries, Storage Rooms, and rooms which function as an intersection with a central fountain or column with torches mounted. There are also unusual rooms with a staircase descending under an arch or bridge against the wall, with another staircase to one side leading up onto this bridge (which rarely allows you to reach anywhere else). While the overall placement and number of these features in the stronghold is completely at random, the features themselves seem to always take the same forms.


 * End portal room, with an end portal and a silverfish spawner.
 * Prison cells seem to be generated in pairs in the wall of a hallway and feature iron doors with or without buttons, and are empty. The doors are usually open.
 * Empty storage rooms are generated off the sides of hallways.
 * Libraries have two sizes: small libraries and large libraries. Small libraries contain bookshelves, wooden Planks, chest(s) and cobwebs dispersed randomly. Large libraries also contain Fences and torches arranged in an upper balcony with a chandelier over the small library, connected by ladders on the far wall from the entrance.
 * Chests can be found on the corner of bookshelves, and on the upper floor of library rooms. They can also be found on the upper floor of 4-way intersections. Chests in libraries may contain paper, books, and/or a compass, and sometimes a map. Intersection chests may contain coal, bread, redstone, iron ingots, Iron Swords, Iron Pickaxes, armor, Ender pearls, diamonds and/or Apples; sometimes chests may contain a very rare item, such as a saddle or a Golden Apple.

Spawning
There is a limit of three strongholds per world. All strongholds are located at random positions in a radius between 640 and 1152 blocks from the origin, 0/0. Due to the generation algorithm, the stronghold may extend further in or out of that area. The three strongholds are spawned at roughly equal angles from the center point of the world (that is, each stronghold is in the region of 120 degrees from the others, measured from the origin.). The game will not generate a stronghold partially above-ground: the portion above the ground layer will be replaced with air blocks, leaving a cutaway. Strongholds are very often broken by caves, ravines, and Abandoned Mine Shafts. They can also be intersected by dungeons. This means that navigating the stronghold can sometimes be very difficult. It also means that it's easy to mine around your home if you decide to live in a stronghold.

A dungeon intersecting a stronghold.

Use as a base
Because of their great size, Strongholds would seem to be a good place to convert into your base. However there are some advantages and disadvantages.

Advantages

 * In SMP, strongholds are difficult for griefers to find, provided they don't use an Eye of Ender.
 * There is lots of space to fill the stronghold with chests
 * There is the possibility of valuable loot in the chests found throughout strongholds.
 * Because strongholds are underground, it's easy to enter an abandoned mineshaft or large cave system and find valuable ore, such as iron and diamond and sometimes, depending on the biome, emerald.
 * The End Portal is nearby so that you do not have to go looking for one.
 * If you become lost above ground, you can find your house using an Eye of Ender

Disadvantages

 * In SMP people might be looking for Strongholds because of the End Portals and therefore find your base.
 * Mining the walls of a stronghold can awaken silverfish, given the presence of silverfish blocks.
 * NOTE: An easy way to detect silverfish blocks is whether or not it takes significantly longer to mine than other blocks of the same type, as silverfish block takes the same time to mine regardless of tools.
 * Strongholds are often split in half by ravines, abandoned mineshafts, and caves, making living difficult unless completely restored.
 * Since the Strongholds usually intersect with ravines or mines, it makes it easier for PVP players that are mining to find your base.
 * You'll either need lots of torches to ensure no mobs spawn in the stronghold, or be constantly alert and ready for a fight.

Trivia

 * End portals may become useless or even completely disappear if there is an Abandoned Mine Shaft or a Ravine cutting through it.
 * Due to the way the overground generates, empty blocks replace any part of a stronghold that exceeds the predetermined ground level, thus making a cross section similar to that seen in the first screenshot.
 * Ravines may cut across strongholds, making navigation difficult.
 * Of all the Stone Brick blocks in a stronghold, approximately 45% are regular stone brick, 30% are mossy stone brick, 20% are cracked stone brick, and 5% are actually Monster Egg blocks.
 * While strongholds are usually quite large, sometimes they can be generated with only a few rooms. An example can be found with seed -6195449077980173317 at -850, 20, -200.
 * Be aware that strongholds frequently spawn underwater, which makes reaching them no easy task.