Start Test Chamber number eleven, then activate noclip mode. (only available in commentary mode) If you fly through the right wall, you should see a green square, it is only visible from above ground level. Fly into it and you will see dancing badgers... more
1.- Go to the test chamber number nine
2.- Use your portal techniques to pass across the glass wall that blocks you to the other side...
3.- when you arrive at the other side, don't pass to the deathly walls near the exit, instead, stay on that... more