1. The quiet-coloured end of evening. The late twilight when the bright colours have faded from the sky.
7. a city. The poet had in mind probably the Campagna,—the level stretch of country outside the city of Rome. This district was once very thickly populated.
9. Supply the conjunctive pronoun, that or which.
13. Notice that throughout the poem, the description of the scenery as it now appears, is alternated with the pictures of its former splendour.
15-8. If there had been trees it would have been an easy matter to distinguish certain slopes from others by the single trees or groups of trees growing on them. Now these slopes are separated only by streams and they take their names from the names of these streams which flow through the valleys.
19. daring. Because it rose so high.
20. like fires. Glittering in the sunlight.
23. nor be pressed. Without being crowded.
29-30. guessed alone, stock or stone. You can only guess that the sticks and stones are there; the grass covers them.