On Chapter 3 (Test Chamber 16) there's a turret tucked away behind a metal railing at the start of the room (on the right). Use the portals and the laser beam to kill the three turrets as per usual, then use a portal to get the beam crossing near the door. Use the reflection cube to kill the turret, opening up the vent. Crawl inside and look down for an impromptu X-Factor audition!
Welcome back to Aperture Science, a world where your Companion Cube isn’t you’re only company. Take control of Chell once again in Valve’s sequel which takes you on an humorous and puzzling adventure and in our detail-packed guide we’ll show you:
How to solve every test chamber first time.
Conquer every co-op chamber with a friend.
Loads of High Definition screenshots and videos showing you the solutions to every single chamber.
High Definition strategy videos for every achievement in the game.
Uncover all of the hidden secrets and Easter eggs.