For this achievement all you need to do is to jump down a hole that is behind a tree and bounce of one of the keys at the bottom. The tree can be found at the top of the waterfall, south of Goatshire. if you follow the path south of Goatshire it will take you to the top of the waterfall when you are up there you should see a girl sitting by one of the tree's, (she is meant to resemble Alice from Alice in wonderland as this achievement is meant to be an Easter egg for Alice and wonderland) behind the tree were she is sitting there should be a hole and if you jump down it and choose yes you would like to travel your achievement should pop when you reach the bottom and bounce of one of the buttons.
This is a very easy 90 G achievement and well worth doing as it only take 2 minuets to complete but If you would like a guide of how to find the hole or a video guide for the whole achievement I have included my video guide below.