Orthanc

[Hot, crispy nice hobbit]

I just noticed a comment by Pippin about the Ent's assault on Orthanic:

'Many of the Ents were hurling themselves against the Orthanic-rock; but that defeated them. It is very smooth and hard. Some wizardry is in it, perhaps, older and stronger than Saruman's Anyway they could not get a grip on it, or make a crack in it; and they were bruising and wounding themselves against it.

How is it that the Numenoreans should built the Tower of Orthanic with impregnable black rock, but construct the outer ring with soft stone? Do they rationalise that if the outer ring is broken, it is still possible to defend the Tower? The Ents had a merry time with the outer fortifications, but the Tower itself, they could not harm... sure tell you something about the Numenorean architecture...

On the other hand, if some "wizardry" is really on the tower itself, then who placed it?