Endgame help please: doors under windmill

[Pesky]

Finished the game. Been in the caves. Seen most things. I still have some doors locked and don't know how to get at the other side.

Under the windmill, I have completed the doors near the movie screen, but there is a door behind me still locked. How do I get at the other side ?

[Pckables]

Hint 1: That area can only be accessed once all 11 lasers are activated
Hint 2: The entrance is in the mountain area
Answer: Look under the yellow box at the top. After, follow the wire to the bottom.

[Pesky]

Thanks for your help. While I have found two exits from the cave complex I haven't found this one. Can you clue me in ? Do I have to solve a puzzle to make it visible ?

[SeniLiX]

Find the challenge room

[Pesky]

Thanks, Pckables and SeniLiX. With your help I found it. There was a little passage at the back of the green cave I walked past without noticing.