Old Forest Road
Of the origins of the Road we know little for certain. We can be sure that it existed before the end of the Second Age, because a record exists of the stone bridge being specially strengthened to carry the armies of the Last Alliance. A strong clue to its origins is presented in its Sindarin name, Men-i-Naugrim, meaning "Dwarf-road". The Dwarves had a tradition of road-building dating back to before the First Age, and it seems that they must have built the Forest Road to carry traffic between their western and eastern clans. It's particularly notable that the old bridge over the Anduin at the Road's western end lay almost exactly halfway between the ancient Dwarvish meeting-place at Mount Gundabad to the north, and Durin's mansions of Khazad-dûm to the south.
Where the Road crossed the Great River, there was originally a stone bridge, but the later years of the Third Age the bridge had been lost and the river was crossed by the Old Ford. From there, a traveller following the Road east would cross some miles of open country before plunging into the depths of the forest. The Road then ran directly east from one side of the forest to the other, covering more than two hundred miles beneath the canopy of trees before it emerged by the banks of the River Running. Beorn warned Thorin and Company that it was often used by Goblins and inside the forest, the road was overgrown and disused; at the eastern end it led to impassable marshes where the paths had long been lost.