Fairy Gold Of Cwmglas Hollow

According to John Rhys in his 'Celtic Folklore Welsh And Manx' [1901] 'The following is a later tale, which Mr. Thomas Davies heard from his mother, who died in 1832:--'When she was a girl, living at Yr Hafod, Llanberis, there was a girl of her age being brought up at Cwmglas in the same parish. The latter was in the habit of saying, when she was a girl and so long as she lived, that she used to have money from the Tylwyth Teg [Fair Folk/Fairies], in the Cwmglas Hollow. Her account was, that on dark, misty mornings she used to go to a particular spot in that Hollow with a jugful of sweet milk from the milking place, and a clean towel, and then place them on a stone. She would return, and find the jug empty, with a piece of money placed by its side: that is, two shillings or half a crown, or at times even more.'

A daughter of that woman lives now at a farm, Mr. Davies observes, called Plas Pennant, in the parish of Llanfihangel yn Mhennant, in Carnarvonshire; and he adds, that it was a tale of a kind that was common enough when he was a boy; but many laughed at it, though the old people believed it to be a fact.

I am not too sure where Cwmglas Hollow is. There is a Cwm Glas Mawr by Llanberis Pass, which is where I have targeted the map below. If anyone can help identify the correct location please do add a comment below.