The Rock is partially based on a fragment of poetry:
The golden cloud slept through the night
Upon the breast of the giant-rock
The piece also draws (according to the composer) from a Chekhov short story in which a man, stuck in a blizzard, tells a young woman the story of his life and his struggles. There is certainly that kind of brooding at work here in this piece...but of course there's brooding. We're talking about Sergei Rachmaninov here.
Here is The Rock.