Silent, reverberant, like some vast shell
Its unknown occupant at last outgrows,
Lies the dark labyrinth. No longer flows
The rushing river whose obstructed swell
Clove these wild ways, and dashed along pell-mell
These rugged rocks, and in its mighty throes
Burst these wide caverns, and in domes arose —
Then, desperate, down these black abysses fell.
All vanished, — save the still, small secret stream
Amid whose gloom the prisoned echoes fly —
And in its empty course we glide to-day,
Glancing like fireflies with the lanterns' gleam,
Strange visitants, to vanish by and by,
As the lost, nameless river passed away.
There are a number of poems about Mammoth Cave, Kentucky. It is said to the the longest cave system in the world.