The Kingdom Under the Mountain

The size of the mountain was about 10 Miles in diameter and it was high enough to be snowcapped at spring and its peak pierced the clouds. There were six spurs radiating from the central peak and in the broad Southernmost vale was the city of Dale. Before Smaug descended and ruined Dale and the dwarf-kingdom the mountain had been clad in threes River Celduin had its spring at the Lonely Mountain inside the front gate to the halls inside the mountain.

Snowcapped > 3,500 feet high (Karen Wynn-Fonstad)

Those lands [about the Lonely Mountain] had changed much since the days when dwarves had dwelt in the Mountain, days which most people now remembered only as a very shadowy tradition. They had changed evenin recent years, and since the last news Gandalf had had of them. Great floods and rains had swollen the waters that flowed East; and there had been an earthquake or two (which some were inclined to attribute to the dragon — alluding to him chiefly with a curse and an ominous nod in the direction of the Mountain). The marshes and bogs had spread wider and wider on either side. Paths had vanished, and many a rider and wanderer too, if they had tried to find the lost ways across. The elf-road through the wood which the dwarves had followed on the advice of Beorn now came to a doubtful and little used end at the eastern edge of the forest; only the river offered any longer a safe way from the skirts of Mirkwood in the North to the mountain-shadowed plains beyond, and the river was guarded by the wood-elves’ king.

— The History of The Hobbit, p. 443

Great traffic of ore between the Lonely Mountain and the Iron Hills.
Presumably iron coming to Erebor and, if ‘between’ implies both ways, then gold ore back the other way?
> So, a (renovated) dwarf-road

The Kingdom Under the Mountain

Dwarves of the Lonely Mountain Osric_of_O Osric_of_O