As you mine in Minecraft- or perhaps even before you mine, by way of finding a ravine- you will encounter caverns. These can come in three different forms- there are natural caverns which tend to be roughly tunnel-like and branch and rejoin all over the place, there are ravines which despite their name can be entirely underground and form huge long clefts in the stone, and there are abandoned mines which contain planks and fences and minecart tracks and often hold torches that light them as well.
Whichever form of open space you encounter underground, you will want to be careful- each of these spaces holds its own dangers, in addition to the ubiquitous threat of wandering monsters.
Natural caverns are dark and often twisted- it’s very easy to lose your way underground in such a cave, and you’ll want to be prepared to clearly mark which way you want to go to get out. As I mentioned in another article about tools, the torch is a very useful item for this purpose. Once you have established a basic way of marking- such as always placing torches on the left so that in order to go back to the surface you simply travel so that torches are to your right- there are other simple placements you can use to both mark and light your way. When you encounter a larger empty space, an effective ‘room’ in the caves, placing a torch on the side wall and another atop a cobblestone block in the center can make sure the whole room is lit without breaking up your marking pattern. When the tunnel branches, you can place two torches- either beside each other or one above the other- on the dividing wall to indicate the split and possibly to indicate which ways the tunnel splits. You can place additional torches in other spots to indicate, for instance, that a tunnel leads somewhere significant, has been mined out of ore, rejoins the other tunnel later, or has something else about it that is remarkable in some way. Always keep in mind, though, that if you leave any area unlit you can wind up ambushed by monsters on your way back through.
Ravines are worse for darkness- but pretty straightforwards. The bottom of a ravine is usually fairly narrow, and if you’re lucky at least some of it will be torch-lit already. There will frequently be single-block paths clinging to either wall of the ravine some distance up from the bottom as well. Because of the way ravines are laid out, there are often large pools of water or lava at their bottom, and long waterfalls or lavafalls down the sides that you will want to either take advantage of or be wary of, respectively. While it’s basically impossible to get truly lost in a ravine because of the way they run in only two directions, it is also basically impossible to keep the whole thing well-lit- ravines are huge vertically, and the tops are wider than the bottoms, meaning that monsters will spawn near the top and gradually make their way down to where you have likely encountered the ravine. This is especially dangerous with skeletons, and encountering a Spider Jockey (a skeleton mounted on the back of a spider) in such a place is a pretty terrifying thought for anyone carrying valuables they want to get back home. Keep your ears sharp for monster noises and look around frequently when you are in a ravine.
Mines are perhaps the least dangerous of the three forms of cave you will find underground, and may turn out to be the most useful. Abandoned mines can reach the surface if they are in the form of a mineshaft, but they may also be simply a network of tunnels branching off of a ravine or cavern. You can identify a mine by several traits- first off, mines are all well-lit and have wooden construction in them. This takes the shape of supports (useless in Minecraft other than as a cosmetic detail) made of wooden fence and plank blocks, often with torches placed on them. Second off, all mines contain minecart track- usually broken up and unevenly placed, but it’s there. Finally, while mines will cut across caverns and into ravines, they will also lead directly to many ore veins that are near them. Abandoned mines are also a good source of string, as you will frequently find the special spiderweb blocks inside them. Unfortunately, this is accompanied by a slightly higher frequency of spiders, but that danger is relatively modest.
When you are traveling through caves, above all else, go at a moderate pace. You never know when a mine or cavern empties out into a ravine with a dangerous drop, or when any of these leads to a sudden pit with lava in it, takes a sudden turn downwards, or when you will run into a dark area full of monsters- such as a spawning room.
