I’ve written before on the theological significance of the sea in Tolkien’s writings, and hence of the tower of Frodo’s dream at Crickhollow which he wanted to climb so that he might look out upon the sea (an image that also occurs in Tolkien’s allegory about the Beowulf poem from his essay). I always assumed that the tower of Frodo’s dream, if it were real, would have been located at or near the Grey Havens. I’ve only just noticed, however, that the tower was in fact real, and that Tolkien references (or presumably does so) in his Prologue to The Fellowship of the Ring.
the Elves of the High Kindred had not yet forsaken Middle-earth, and they dwelt still at that time at the Grey Havens away to the west, and in other places within reach of the Shire. Three Elf-towers of immemorial age were still to be seen on the Tower Hills beyond the western marches. They shone far off in the moonlight. The tallest was furthest away, standing alone upon a green mound. The Hobbits of the Westfarthing said that one could see the Sea from the top of that tower; but no Hobbit had ever been known to climb it. Indeed, few Hobbits had ever seen or sailed upon the Sea, and fewer still had ever returned to report it. Most Hobbits regarded even rivers and small boats with deep misgivings, and not many of them could swim. And as the days of the Shire lengthened they spoke less and less with the Elves, and grew afraid of them, and distrustful of those that had dealings with them; and the Sea became a word of fear among them, and a token of death, and they turned their faces away from the hills in the west. (Fellowship 16)
We’re not told exactly that this is the same tower as in Frodo’s dream–Frodo’s tower is white, but no mention is made of its color here, and while the Grey Havens tower is “alone on a green mound,” Frodo’s tower is “standing alone on a high ridge.” The fact, however, that it is singled out by Tolkien as the one from which the Hobbits believed they could see the sea, and yet “no Hobbit had ever been known to climb it,” would seem to be pretty conclusive that this is one and the same tower.
Frodo dreams of the tower even though he’s never seen it, but he’s surely heard about it. Elsewhere in Tolkien’s stories, however, when someone dreams of a place or an experience they have not personally encountered, it’s because they’ve inherited the experience from either an ancestor or possibly from the immediate environment itself–see, for example, Faramir’s dream of the tidal wave destroying Numenor and Merry’s inherited memory at the Barrow-Downs. (For more on inherited memory, see this resource and this.) Is it possible Frodo is having his own, inherited-memory experience in his dream of the tower and desire to see the sea?