O'Bannon's early Alien script: Online version: Inside the Pyramid scene:

  INTERIOR - PYRAMID - DAY

     Broussard resumes his downward climb.  SUDDENLY, HIS FEET LOSE THEIR
     PURCHASE AS THE WALLS OF THE SHAFT DISAPPEAR.

     The tunnel has reached its end.  Below him is an unfathomable,
     cavernous space.

                              BROUSSARD
                    (huffing and puffing)
               Tunnel's gone -- cave or something
               below me -- feels like the tropics
               in here; air is warm and humid... 
                    (consults his instruments)
               ... high oxygen content, no dust,
               it's completely breathable --

     Puffing with exertion, he releases his purchase on the stone walls and
     begins to lower himself on power.  Now he is dangling free in darkness,
     spinning slowly on the wire as the chest unit unwinds.

     Finally, his feet hit bottom.  He grunts in surprise and almost loses
     his balance.

     INTERIOR - TOMB - DAY

     Broussard is standing on a dusty stone floor, with a feeble column of
     sunlight shining down around him from the tunnel above.  Around is
     solid darkness.

     He flashes his datastick around.  The beam reveals that he is in a
     stone room.  STRANGE HEIROGLYPHICS are carved into the walls.  They have
     a primitive, religious appearance.  Row after row of pictograms stretch
     from floor to ceiling, some epic history in an unknown language.  Huge
     religious symbols dominate one wall.

     Spaced at intervals are stylized stone statues, depicting grotesque
     monsters, half anthropoid, half octopus.

                              BROUSSARD
               It's unbelievable!  It's like some
               kind of tomb... some primitive
               religion!  Hey, is anybody there?  Do
               you read me?  Standard!

     Annoyed, Broussard yanks off his breathing goggles, and leaves them
     hanging around his neck.  He takes a deep breath of the wet air.