YOU ARE IN A DEBRIS ROOM FILLED WITH STUFF WASHED IN FROM THE SURFACE. A LOW WIDE PASSAGE WITH COBBLES BECOMES PLUGGED WITH MUD AND DEBRIS HERE, BUT AN AWKWARD CANYON LEADS UPWARD AND WEST. A NOTE ON THE WALL SAYS "MAGIC WORD XYZZY".
A THREE FOOT BLACK ROD WITH A RUSTY STAR ON AN END LIES NEARBY.
The black rod is used to magically create a bridge across a deep chasm which you will need to cross eventually.
You can go back to the grate. Or you can leave the cave. Or you can go back through the cobble crawl. Or forward through an awkward sloping east/west canyon. Or forward past the canyon to a pit. Or use magic to go back to the building.XYZZY.