does anyone know how to get to the ROTT 2013 secret level Escape from the Vomitorium? I've seen video walkthroughs of the level itself but never ANY that tell you how to get to it. (I think its the episode 4 secret level)

seriously, does anyone know how to get to the vomitorium? it looks like a kick ass level but I don't know where to go to find it in whatever level