Trackway approximately 6km long across moorland from Cwm Rhiwarth NW over Rhiwaedog-is-afon via the western flank of Foel Cwm Sian Llwyd, towards Plas Rhiwaedog. Probably of medieval origin. It is recorded in the RCAHMW Inventory with the suggestive name 'Sarn', but tthere is no evidence for a Roman road here.

On the S side of Foel Cwm Sian Llwyd it is mainly a narrow path, except for the SE end where it is a sunken track in a depression up to 10m wide and 1.8m deep. This section was used in the C19 to carry peat from the hill.

The section further NW that crosses Rhiwaedog-is-afon is better preserved, partly as a 2m wide ledge in the hillside, partly as a sunken track 0.5m deep.

RCAHMW, Inventory vol 6: Merionethshire, 1921, p 118.
Recorded as part of Uplands Initiative Survey. R Hayman, H&H, 16/12/2010.