The river assuaged
Years cut through limestone.
For anyone interested in this form, which is quite similar to a haiku (though poses a different challenge), this is known as the Kelly Lune. A variation of the Lune created and popularised by the poet Robert Kelly.
After much experimentation, he settled on a 13-syllable, self-contained poem that has 5 syllables in the first line, 3 syllables in the second line, and 5 syllables in the final line.