I found the secret place! On my second time through, that is. I had fun with it, and the puzzles were very intuitive the second time around. Also. the names are helpful hints.
OH! And are the gameplay mechanics the same as Portal's, where through each doorway is actually an identical map, connected on a different point? If so, how many alternate maps are going at once? Is it just two? Or is it only one, using some other mechanic?