The dark lord sits in the tower and looks over the dark seas and the dark world [and] his hand stretches over the cold sea and the dead world.

This quote just blows me away. It is from Return of the Shadow (HoME, VI), an early draft of the story of the Barrow Downs (I think in the final draft the line is reduced to ‘till the dark lord lifts his hand’).

Now, it is here suggested that Elostirion, the Elf-tower on the Tower Hills (Emyn Beraid) west of Hobbiton, was the original tower out of which was unfolded Orthanc (by way of Frodo's dreams).

Consider, then, this quotation from 'The Tower of Cirith Ungol' in Return of the King:

The Shadow that bred them can only mock, it cannot make: not real new things of its own.

Frodo is here speaking about Orcs. (He continues: 'I don’t think it gave life to the orcs, it only ruined them and twisted them...').

But perhaps the same could be said about towers and vision itself? In which case Elostirion, once home to the Seeing-Stone (the Palantír that looks West, over the sundering sea, back to Faërie) becomes the original, not only of Orthanc, but also of Barad-dûr, where dwelled the Great Eye of Sauron.