Misty Mountains
There must must once have been some sort of path leading south from Rivendell along the foothills of the Misty Mountains at least as far as Eregion, since Elves dwelt there too. (The Ring Goes South; Bk 1). Possibly it went on to join the Old North Road between Tharbad and the Gap of Rohan. The travellers came up this way on their road home from Minas Tirith when their adventures were over.
On their outward way, however, the Companions avoided this path, so as to keep out of sight. (The Ring Goes South; Bk 1). It took them a fortnight to travel between Rivendell and Eregion – a distance of 135 miles as the crow flies