A Ravine is a type of naturally-generated, eroded landform added to Minecraft as part of update 1.6. Ravines are very similar to open-surface caverns, and they can be found in all Biomes except Desert, Tundra, or Mushroom Island.
Ravines are large chambers that extend beneath sea level. Many ravines are located below the surface of the Overworld, with the top completely covered by a few layers of stone or dirt. However, some ravines can be located above ground, completely exposed to the sky above. Many ravines have the potential to be up to 40 blocks deep, and they are approximately five blocks wide. On occasion, one ravine may connect to or intersect with another. Ravines also almost always connect to at least one cave system. Despite it being a rarity, ravines have the potential to be spawned underwater, forming a peculiar type of blue hole.
Due to how the map generator adds ravines to the game, ravines can also intersect Abandoned Mine Shafts, Caverns, and Strongholds. Typical finds in a ravine can be Lava or Water, along with Ore Veins, the most common of which are veins of Coal and Iron. Sometimes, Lapis Lazuli can be found in small quantities. Ores can generally be located in patches scattered across the wall. These ores can usually be collected by naturally generated ridges that travel along the walls; these can be reached by stair-casing to them or building a bridge from one to another. Ravines usually are found connected to caves, and if explored further, an abandoned mineshaft.