Object -> cage "iron cage"
  with name "iron" "cage" "bars" "barred" "iron-barred",
       when_open
          "An iron-barred cage, large enough to stoop over inside,
           looms ominously here.",
       when_closed "The iron cage is closed.",
       inside_description "You stare out through the bars.",
  has  enterable container openable open transparent static;