In dictionaries:
Bryn Celli Ddu
a prehistoric site on the Welsh island of Anglesey located near Llanddaniel Fab.
Ogof Ffynnon Ddu
Ogof Ffynnon Ddu (Welsh for cave of the black spring), also known informally as OFD, is a cave under a hillside in the area surrounding Penwyllt in the Upper Swansea Valley in South Wales.
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