How big was Ancalagon?

[Nerwen]

Originally Posted by Lalaith

I know its a bit blasphemous but think of Merlin - of the Dragon crashing down on Camelot and breaking the towers. It would happen. I agree with Morthoron, that the "towers" were constructions of Morgoth, not of nature.

Actually, we know they were constructions– but that doesn't make them buildings in the normal sense:

Originally Posted by Vultur

The towers as buildings: possible. But elsewhere 'the towers of Thangorodrim' clearly means the mountain peaks: Morgoth raised them as slag-heaps, etc.

And this seems to be quite true. However, by the same token–

Originally Posted by Vultur

Yes, but I don't think you can break Everest with a blue whale, even if you drop it from space.

I can't recall any indication they were anything like as high as Everest, and they weren't natural mountains, so maybe they wouldn't be all that stable. Ancalagon would still have to be utterly enormous, however.

As has been said already, though, the account in the War of Wrath should perhaps not be taken too literally.