Here are some possible interpretations:
* A physical object: It could be a doorway, a tunnel, a staircase, or even a simple crack in the earth.
* A metaphorical concept: It could represent a lost opportunity, a forgotten path, or a hidden source of strength.
* A specific historical event: Depending on the context, it could allude to a buried city, a lost civilization, or a forgotten battle.
The beauty of this poem lies in its ambiguity. It sparks the imagination and encourages each reader to find their own meaning within the verses.