sentences:  Prior to 1860, Gilfach Goch was an area of mountain land situated in the Ogwr Fach valley in the parish of Ystradyfodwg far north of present-day Gilfach.Ordnance survey maps have shown that the name Gilfach Goch is not only the name of the community that sprang up with the coming of coal, but the hill and a strip of land on the east bank of the Ogwr Fach.This section of the Ogwr Fach valley is very narrow and lends itself to the description "cil"-"fach", but is also home to a tributary of the River Ogwr whose bed contains iron ore.