There is 22km coastal strip of sand dunes which extend almost continuously from the Mawddach Estuary in
Barmouth
in the South, to Morfa Bychan, Porthmadog in the North.
Two areas along this strip, Morfa Harlech and Morfa Dyffryn, are designated National Nature Reserves
Taken together the large beach
Traeth Mawr (pictured above) and Small Beach
Traeth Bâch which make up Morfa Harlech account for some 11km.
The fact that the castle was provisioned by sea while the castle was under continuous siege for 7 years and the many ‘ynys’ placenames meaning 'island' testify to the fact that most of the area forming Lower Harlech and to the North of Lower Harlech was in fact covered by sea.
