This will be the first achievement you earn.
To obtain this, and escape the cave, you will need to head right until you reach a stalagmite that is blocking your path. Examine it and head back to the left to the pile of rocks. Pick up a rock and then use it on the stalagmite to break it down. Pick up the stalagmite and head right. You will find a hole in the wall that is a too small to fit through. Use your stalagmite on this hole and an exit will be created. Leave the cave to earn this achievement.