The Waste Land
You'll probably never find a poem more packed with references to art, culture, and history than this one. The thing is practically made up of lines from other literary works (see the "Allusions" section and the "Summary" to get a sense of just how crazy-extensive these references are). On top of that, you've also got Eliot's trademark dreariness, which he somehow manages to convey with some of the most beautifully written poetry you'll ever read.
Eliot is especially on his game when he's writing about dust, bones, and wind, a trio of images that he'd nearly perfect two years after "The Waste Land," when he wrote "The Hollow Men." Only Eliot could write something like, "But at my back in a cold blast I hear / The rattle of bones, and chuckle spread from ear to ear" (185-186), or "I will show you fear in a handful of dust" (30).