The Boulder Cave's entrance is shaped like a pentagon, with its interior sharply shifting to the far left. The obstacle will end when the player is inside any part of the cave. There is a wall in the start of the cave and if 50% or more of the player is in the cave.
In the top-right corner of the ceiling of the cave, there is a small gap in which light will pour out of. If the player manages to get out of the hole, they will drop down to the Underground Grove.
The Boulder Cave is the source of all the boulders that roll down the Volcano Obstacle whenever a player is present inside the Volcano. These boulders are generated to give more challenge and difficulty to the Volcano Obstacle.