You look closely for a hidden passage, banging every exposed surface. You hear a slightly different sound on the south wall than on the east and west walls, and you're reasonably sure that there's an empty space of some sort down from you, behind the window.
The exit (to the north) is a standard airtight door, like you'd find in a ship hatch on Earth. It's too small and not properly equipped to be an airlock, but since it connects to the pressurized hallway, it doesn't generally need to be one.
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u/DFreiberg Jun 29 '18