What sprung to mind was the ruins of Roman Civilization in Britain… Far away from the hub, where the histories were still kept, the Anglo-Saxons invented legends of a race of giants who could build and support such monumental things.

I would assume that this is what Tolkien used as his model for the various ruins of the Dúnedain, which the party keeps running across. The Argonath, The Tower of Amon Sûl, places of former majesty of the Dúnedain, who themselves are descendants of the Númenóreans, now lost to the world…

Watch closely as history becomes legend, and legend becomes myth…