I know the map's effectively upside-down, but this is how it was published.
Yellow shows the areas where we pointed our torches and walked forward:
Trees. A lovely day for messing around in woods. Badger... badger... mushroom... snake!
Cold Tunnels. And suddenly everything goes black.
Blast Door. Entering the shelter proper.
Proper Tunnels. And we finally reached the tunnels proper.
Sick Bay. Or canteen. Whatever.
Ventilation Shaft. Daylight at last.
Crapola. It's jumble day in the tunnels. Lots of bric-a-brac for taking!