Sinkhole

The sinkhole (also referred to as the pit, the crater, or simply the big hole) is an environmental feature added in v0.16. It was not mentioned in the patchnotes, so the sudden appearance of it surprised many players.

Reaching the Bottom
There are multiple ways to reach the bottom of the sinkhole. To get to the bottom you can:
 * 1) Go through Cave 7, which will open up a pair of sacrificial doors at the bottom of the sinkhole, allowing the player to walk straight in.
 * 2) Jump from the highest cliff straight on the pond in the center of the sinkhole; you'll maybe have to do a lot of attempts before to get it.
 * 3) Jump/slide down ledges on the walls. This is very dangerous, and the player will likely sustain serious, possibly fatal injuries as he proceeds; meds and other healing items are necessary. This method is often used in speed runs.
 * 4) Build a set of stairs. This is a very time-consuming option. As of v0.70, the sinkhole has an invisible layer with a few ferns growing on it. It cannot be bypassed with a log sled, which will just hang in the air on top of the invisible barrier; the only way to deliver the needed materials is to carry logs down under the barrier layer.
 * 5) Use the climbing axe to help climb down. At the sides of the sinkhole, a few places have areas you can attach your climbing axe. The area with the tents, halfway down the sink hole is one of these areas. As of v1.09 there are very few areas in the sinkhole where the climbing axe can be used, however.
 * 6) Building a freestanding zipline across the sinkhole. Use it and let go when you are halfway across the sinkhole (about 6 seconds on the zipline). If you time it right, you will land in the center where the water is.
 * 7) Use the turtle shell as a sled and ride down the slopes.(Patched*: No longer a reliable option; it is still possible to ride down the walls, albeit it is now rather difficult, and you will take a lot of damage if you do make it.)
 * 8) Use a glider, spinning to lose altitude progressively without running into the walls.
 * 9) In multiplayer, fall damage can be cancelled by landing on top of a downed ally. Incredibly hard to pull off, but by landing on any downed ally you can cancel the fall damage and resurrect them, leaving you both alive at the bottom.

Contents
Fully exploring the sinkhole is required to complete the story. The location contains the entrance to Cave HC, which leads to the Sahara Research Laboratory and the end of the game. The player will need, among other things, the keycard, climbing axe, and rebreather to fully explore the sinkhole.

There are large rock formations scattered throughout the bottom of the sinkhole, along with a couple of small waterfalls on the north and southeast sides. Multiple creepy mutants and several regular cannibals wander around the sinkhole floor in close proximity to each other, making it one of the most dangerous areas in the game. There are usually 4+ pale mutants, 1-2 armsies, and 2-3 (as of v1.09) cowmen. These cannibals will spawn no matter the game mode (Normal or Hard).

Near the sacrificial doors, there is also a crashed helicopter; the machete may be found just outside the cockpit.

Some flat cardboard boxes and wooden crates scattered around contain circuit boards and other supplies.

Combat
The rocks at the bottom of the sinkhole form walls that direct the player along around the bottom. Luckily, they are climbable if the player can find a low spot to jump up (such as somewhat near the sacrifice doors). Once on top of the rocks, the cannibals below are easy pickings. Simply use the flare gun, flaming arrows, or molotovs. Do note that if the player remains on the low spot on the rocks, the cannibals and mutants can and will charge or jump up.