Go thou to Rome—at once the Paradise, The grave, the city, and the wilderness; And where its wrecks like shatter'd mountains rise, And flowering weeds, and fragrant copses dress The bones of Desolation's nakedness Pass, till the spirit of the spot shall lead Thy footsteps to a slope of green access Where, like an infant's smile, over the dead A light of laughing flowers along the grass is spread;
Go to Rome, he again commands. He has a few more reasons for mourners to visit the city.
It's many things at once: it's a paradise (because it is beautiful), it's a grave (because so many are buried there), it's a city (that one speaks for itself), and it's the wilderness (because parts of it are still wild).
Plus, the ruins of the Roman empire still poke through the weeds, and they look like "shatter'd mountains."
Seeing those ruins is another reason to go, according to the speaker. Why? He calls these ruins the "bones of Desolation's nakedness." That's a pretty striking image, wouldn't you say? The fragments of old buildings, like the Coliseum, are pale like bones.
This image also works as a metaphor: like bones, the ruins once were the structure and support of something larger.
As you walk through these ruins, he says, you'll come upon another reason to go to Rome: Keats is buried in a green, flowery place, pure as an "infant's smile."