Bombadil's brooch

[Raynor]

It seems to me that there were other buildings in/around Tyrn Gorthad, which could have been the actual refuge places, besides the ancient graves:

Originally Posted by In the house of Tom Bombadil, FotR

[The hobbits] heard of the Great Barrows, and the green mounds, and the stone-rings upon the hills and in the hollows among the hills... Green walls and white walls rose. There were fortresses on the heights. Kings of little kingdoms fought together, and the young Sun shone like fire on the red metal of their new and greedy swords. There was victory and defeat; and towers fell, fortresses were burned, and flames went up into the sky.