Two climbers reach the summit of a peak and, instead of rushing on, simply stop. The poem opens on that pause: they "stand still / in the height" of their wish to see other peaks. The want that drove them upward doesn't fade once they arrive. It stretches outward toward the next horizon.
The mood is quiet and a little awestruck. The mountains are described as "still" and "old," and the repetition of "old" makes them feel almost beyond time. Against that calm, the last lines turn to the body, which is "singing / with pain." That image is surprising, since it makes the aching of the climb sound like music. The speaker seems to feel two things at once: the vast, silent permanence of the land and the loud, fleeting aliveness of a tired body. Judging by the poem's shape, the climb is less about conquering a summit than about feeling small, worn out, and strangely glad.