You see it from above the Video Projector room, on that walkway.

You have to be watching the first (leftmost) video to see it. The one with James Burke talking and occasionally showing pictures.

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This solution combines one of those odd things with the content of an actual video.

Start the first video, and run through the caves until you're up on the walkway above the Video Room.

There will be a point where the video shows a circle that's the same basic color and texture as the tan/gold stuff that's hanging around on the walkway.

Trace it quickly, and be ready to try again.

(You can save time by fast forwarding and rewinding through the video using the panel where you first drew the path to start the video.)

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This takes some timing.

This one is underground.

You might have noticed some oddly shaped or colored things when you were in the Video Projector room watching videos.

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See that big hole off to the side of town? Look down it and you'll see that you're above the Video Projector room. But you'll also see that there's a walkway (catwalk) below you that crosses over the room.

If you haven't stood on that yet, then you can't solve this puzzle.

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You actually can't get to that walkway until very late in the game. For one thing, you have to have solved all 11 lasers.

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Explaining how solving 11 lasers helps you get to that walkway would give pretty big spoilers for the game. But if you do solve all 11 lasers, head into the mountain and figure out what 11 lasers get you that you didn't get from just the first 7 lasers.

And you might as well stop reading here.

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And you have to be standing on the walkway above the Video Room while you're watching.