Unlike most structures, Strongholds are intended to be difficult to locate through conventional means, providing almost no outward indication to exposed areas; though they are often intersected by cave systems and Abandoned Mines.
Strongholds vary in size but are generally large and complex, containing multiple rooms, corridors, stairwells, doors, and other features. Strongholds each contain a 'portal room' with an unactivated End Portal, which can be activated with twelve Eyes of Ender, for travel to The End.
Strongholds vary in size. They contain several doors and rooms made mostly of Stone Brick, Mossy Stone Brick, and Cracked Stone Brick. Strongholds are lit by enough torches to provide visibility in most areas, though not enough to suppress mob spawns.
Each Stronghold contains several dispersed Chests. These can contain any of the following: Paper, Redstone, Books, Enchanted Books, Coal, Gold Ingots, Iron Ingots, Compasses, Apples, Golden Apples, Ender Pearls, Iron Chestplates, Iron Boots, Iron Pickaxes, Iron Helmets, Iron Leggings, 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. Strongholds contain regular mobs that spawn under normal conditions, as well as Silverfish that are created when someone either mines one of the blocks within, or finds the End Portal room, which contains a Silverfish Spawner.
Strongholds feature various types of main rooms. While the overall placement and number of these is completely random, the features themselves seem to always take similar form.
- End portal room: Contains an unactivated End Portal and a Silverfish Spawner.
- Empty prison cells: These seem to be generated in pairs within the walls of a hallway, and feature iron doors (with or without activating buttons). These doors can be open or closed.
- Empty rooms: Small rooms generated off the sides of hallways.
- Fountain rooms: These contain a fountain in the center, which consists of stone pillar with a water source block on top.
- Store rooms: Dual-level rooms with a cobblestone center structure joining the two. A lone torch is housed within the structure. A ladder runs up the side wall for access to the second floor, which is made of wood planks and contains a Chest. This chest can contain: coal, bread, redstone, iron ingots, iron swords, iron pickaxes, armor, ender pearls, diamonds and/or apples. More rarely, it can also contain very rare items, such as a saddle or a golden apple.
- Libraries (see below).
Large libraries contain a second level consisting of a surrounding balcony with Fences as railings, and fences/torches arranged in a chandelier formation over the center of the room. The two levels are connected by ladders on the wall furthest from the entrance.
Chests are found on the corner of one bookshelf in each library, with an additional Chest in the corner of the top floor in duplex libraries. These can contain paper, books, and/or a compass, and more rarely, a map.
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 world's original spawn point, at 0/0 (but 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: any portion above the ground layer will be replaced with air blocks, leaving a cutaway.
 Use as a base
Because of their great size, Strongholds would seem to be a good place to convert into your base. There are advantages and disadvantages to doing this.
- 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
- 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.
|1.8||Added strongholds as part of Adventure Update. They are vacant except for regular mobs that spawn under normal conditions. In early screenshots, they were at surface level; this is now extremely rare.|
|1.9pre1||The End Portal room was added to the Stronghold for the Skyland which was scrapped in Beta 1.9 Pre 4.|
|1.9pre3||A pair of glass towers indicated the location of a Stronghold's start (aka Main entrance) and second for the portal room on top of them, extending from the top of the map to the stone bricks. This was because Jeb forgot to remove the debug towers.|
|1.9pre4||Removed glass towers generating above strongholds.|
|1.4.2||12w40a||Strongholds can now spawn in the air in Superflat worlds with certain customization presets.|
Four silverfish chasing the player in a stronghold.
- End portals may be incomplete due to mineshafts or ravines generating through them, or occasionally disappear completely. In any case, if not complete, they will become useless, which can be problematic in a single player survival game.
- 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 but locating them easier.
- 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, some can be generated with only a few rooms.
- Strongholds usually spawn underwater, meaning reaching them is difficult, and whole rooms can be flooded if the stronghold is intercepted by a mineshaft or ravine.
- There is also on average one room with Cobblestone Stairs in every Stronghold.
- There can possibly be only one eye of ender in one of the portal frames, and as many as six.