it looks to me like they have reached Erech, not Dwimorberg, as you claimed before.

At last the king’s company came to a sharp brink, and the climbing road passed into a cutting between walls of rock, and so went up a short slope and out on to a wide upland. The Firienfeld men called it, a green mountain-field of grass and heath, high above the deep-delved courses of the Snowbourn, laid upon the lap of the great mountains behind: the Starkhorn southwards, and northwards the saw-toothed mass of Irensaga, between which there faced the riders, the grim black wall of the Dwimorberg, the Haunted Mountain rising out of steep slopes of sombre pines. Dividing the upland into two there marched a double line of unshaped standing stones that dwindled into the dusk and vanished in the trees. Those who dared to follow that road came soon to the black Dimholt under Dwimorberg, and the menace of the pillar of stone, and the yawning shadow of the forbidden door.

Such was the dark Dunharrow, the work of long-forgotten men. Their name was lost and no song or legend remembered it. For what purpose they had made this place, as a town or secret temple or a tomb of kings, none could say. Here they laboured in the Dark Years, before ever a ship came to the western shores, or Gondor of the Dúnedain was built; and now they had vanished, and only the old Púkel-men were left, still sitting at the turnings of the road.

Merry stared at the lines of marching stones: they were worn and black; some were leaning, some were fallen, some cracked or broken; they looked like rows of old and hungry teeth. He wondered what they could be, and he hoped that the king was not going to follow them into the darkness beyond