Just thought of something else.

When Boone and Locke first found the hatch, it was partially covered, in a ravine.

Could those topographical features in the wall diagram be ravines or valleys, and not rivers?

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charlie98210
"Whoa!" she said. "Cry 'Havoc!' And let loose the dogs of war!"
And, like Banquo's ghost, they just won't go away.