The Return of the King
How we cite our quotes:
Pippin gazed in growing wonder at the great stone City, vaster and more splendid than anything that he had dreamed of; greater and stronger than Isengard, and far more beautiful. Yet it was in truth falling year by year into decay; and already it lacked half the men that could have dwelt at ease there. In every street they passed some great house or court over whose doors and arched gates were carved many fair letters of strange and ancient shapes: names Pippin guessed of great men and kindreds that had once dwelt there; and yet now they were silent and no footsteps rang on their wide pavements, nor voice was heard in their halls, nor any face looked out from door or empty window. (5.1.37)
It looks like Boromir had it right all the way back in The Fellowship of the Ring Book 2, Chapter 2. Minas Tirith is suffering from some serious urban decay. The City is a strong tower against the darkness—a "great stone City, vaster and more splendid than anything that he had dreamed of," sure. But the Gondorians are only at half strength, and they no longer have the ability to withstand Sauron with these depleted numbers. Pippin sees signs of "great men and kindreds that had once dwelt there" — but where are they now? The lords of Gondor are dying out, and with them dies the hope of renewal. That is, until a certain king comes a'knocking.
Merry got up and yawned. His few hours' sleep had not been nearly enough; he was tired and rather dismal. He missed Pippin, and felt that he was only a burden, while everybody was making plans for speed in a business that he did not fully understand. (5.2.35)
Merry is now in the exact same position in which we found Pippin in Book 5, Chapter 1: he has come along for the ride to Helm's Deep (as Pippin did with Gandalf to Minas Tirith), but he doesn't really know what he's doing here, what's going on, or what help he can be. He has to find a purpose. But considering Aragorn has already told Merry that his fate rests with Théoden, and that Pippin has already sworn an oath to Lord Denethor, we think we can guess where our Merry is headed. If he's in the same position that Pippin was in in the previous chapter, it stands to reason that he, too, will swear an oath to someone—say Théoden?—in the near future, just to give himself something to do, and something to fight for.
Such was the dark Dunharrow, the work of long-forgotten men. Their name was lost and no song or legend remembered it. For what purpose they had made this place, as a town or secret temple or tomb of kings, none in Rohan could say. Here they laboured in the Dark Years, before ever a shape came to the western shores, or Gondor of the Dúnedain was built; and now they had vanished, and only the old Púkel-men were left, still sitting at the turnings of the road. (5.3.23)
There are a ton of ruins scattered over Middle-earth. Weathertop, Amon Hen, Osgiliath—all of these places contain signs of old settlements or cities that have since been abandoned or overrun by enemies. What makes the Púkel-men interesting and different from these other ruins is that these statues are so ancient that no one knows where they even come from, and that's a rare thing in history-conscious Middle-earth. And without a proper name, they lack of the force of the Argonath or Osgiliath. When Aragorn looks at the Argonath, he sees his forebears, the kings of Gondor. But the Púkel-men have no such power over anyone living. They are simply puzzles or curiosities, like Stonehenge. Without an origin story, they have no power over Middle-earth imaginations. But still, these statues persevere.