Glannau Porthaethwy is a designated Site of Special Scientific Interest (SSSI) along the northern shore of the Menai Strait in

North Wales North Wales ( cy, Gogledd Cymru) is a region of Wales, encompassing its northernmost areas. It borders Mid Wales to the south, England to the east, and the Irish Sea to the north and west. The area is highly mountainous and rural, with Snowdonia N ...

. It is a linear designation that extends some along the shore from

Britannia Bridge Britannia Bridge ( cy, Pont Britannia) is a bridge across the Menai Strait between the island of Anglesey and the mainland of Wales. It was originally designed and built by the noted railway engineer Robert Stephenson as a tubular bridge of w ...

in the west to Craig y Don in the east. It also includes the island shorelines of

Ynys Gorad Goch Ynys Gored Goch ("Red Weir Island"), sometimes Ynys Gorad Goch, is a small island in the Menai Strait between Gwynedd and Anglesey in north Wales. It is situated in the stretch of the strait called the Swellies between Thomas Telford's Menai Sus ...

, Ynys Welltog, Ynys Benlas, Ynys Tysilio, Half Tide Rock, Ynys Faelog, Ynys Tobig,

Ynys Gaint Ynys Gaint is a small island in the Menai Strait connected to the town of Menai Bridge on Anglesey by a causeway (which still exists today) and also a concrete bridge erected by Sir William Fison (a previous owner of the island) in the 1930s. ...

Ynys Castell Ynys Castell () is a small (1.6 acres at high tide) island in the Menai Strait which separates Anglesey and mainland Wales. It is an extruding piece of Precambrian schist lying to one side of the Afon Cadnant estuary. It lies between Ynys y B ...

and Ynys y Big. It was designated in 2003, as it is the most extensive sheltered rock shore in the area between

Bardsey Island Bardsey Island ( cy, Ynys Enlli), known as the legendary "Island of 20,000 Saints", is located off the Llŷn Peninsula in the Welsh county of Gwynedd. The Welsh name means "The Island in the Currents", while its English name refers to the "Islan ...

and

Great Orme The Great Orme ( cy, Y Gogarth) is a limestone headland on the north coast of Wales, north-west of the town of Llandudno. Referred to as ''Cyngreawdr Fynydd'' by the 12th-century poet Gwalchmai ap Meilyr, its English name derives from the Old N ...

’s Head and because it supports the greatest diversity of marine plant and animal communities.

References

Cwm Cadnant Llanfairpwllgwyngyll Menai Bridge Menai Strait Coast of Anglesey Sites of Special Scientific Interest on Anglesey {{UK-SSSI-stub