A Nether Fortress is a large structure found in the Nether, a dangerous dimension in the game Minecraft. These fortresses are made of dark bricks and are characterized by their long hallways, bridges, and staircases. They often contain valuable resources and unique mobs, making them important locations for players to explore. Inside a Nether Fortress, players can encounter Blazes, which are fiery creatures that drop blaze rods, and Wither Skeletons, which can drop valuable skulls. The fortresses also contain Nether Wart, a crucial ingredient for brewing potions. Exploring these structures can be both rewarding and challenging due to the hostile environment.