North Stack

Caer y Twr (meaning 'fort of the pile/heap') is an Iron Age hillfort atop the summit of the Holyhead Mountain in Anglesey, Wales. The hillfort, which is situated among rocky outcrops, is ideally placed for defence and likely served as a watchtower and possibly as a signal tower. Some have speculated that it was built to alert a small fort in the modern town of Holyhead in the case of raiders coming in from the Irish Sea, while others have suggested that it may have been a lighthouse. The hillfort is now mostly rubble, but its walls can still be made out, including a large stone rampart on the north and east sides which reaches 3 metres at points. The entrance to the fort was through a rocky gully. The footings of a tower were discovered when the site was excavated; its stones are believed to date from the 2nd to the 4th centuries. Nestled below Caer y Twr is a group of several enclosed huts, named Cytiau Tŷ Mawr (the Holyhead Mountain Hut Circles), that also date from the 3rd to the 4th centuries, some of which still contain the accoutrements of life, such as hearths and shelves.

Holyhead Mountain (Welsh Mynydd Twr, from mynydd 'mountain, unenclosed land' and twr 'a heap, pile') is the highest mountain on Holy Island, Anglesey, and the highest in the county of Anglesey, north Wales. It lies about two miles west of the town of Holyhead, and slopes steeply down to the Irish Sea on two sides. Ireland can be seen from here on a clear day and the mountain is an important site for seabirds.

The Holyhead Mountain Hut Circles, also known as 'Tŷ Mawr Hut Circles', Cytiau'r Gwyddelod or the 'Irishmen's Huts', are the remains of a group of Celtic Iron Age huts near Trearddur on Holy Island, Anglesey, Wales. The site is under the care of Cadw and can be visited all year round. The construction of these huts are very similar to those at Din Lligwy, having thick stone walls.

The Holyhead transmitting station was a broadcast television facility located about 2.5 km to the west of Holyhead, on Anglesey, Wales. It had a self-supporting 30 m lattice mast erected on land that is itself about 76 m above sea level. The site was originally built by the BBC, entering service in early 1964 transmitting the now-defunct 405-line VHF television system. When UHF 625-line colour TV came to north Wales in the 1970s, the locality fell into the service area of the main transmitter at Llanddona or the relay at Arfon and so this site was not needed as a repeater. 405-line television from Holyhead was shut down in January 1984. The site appears to have been demolished subsequently.

Llaingoch (Welsh pronunciation) is an area of Holyhead in North Wales that lies between the town centre and Holyhead Mountain. The name comes from the Welsh llain, plot or patch of land, and goch, red.

Goferydd is an area in the community of Trearddur, Ynys Môn, Wales, which is 141.4 miles (227.5 km) from Cardiff and 228.9 miles (368.4 km) from London."Goferydd" is a Welsh word meaning "overflowing."

South Stack (Welsh: Ynys Lawd) is an island situated just off Holy Island on the northwest coast of Anglesey, Wales.

Elin's Tower (Welsh: Tŵr Elin) is a Victorian stone tower on Holy Island, located around 2+1⁄2 miles (4 km) west of Holyhead. The castellated folly, which was originally used as a summer house, was built between 1820 and 1850 for the notable Stanley family from Penrhos. It is named after Elin (anglicised as "Ellen"), the Welsh wife of the 19th-century politician William Owen Stanley.The building near South Stack was used during both the First and Second World Wars as a coastal observation tower. However, it was abandoned and fell derelict. The restored tower is used as an RSPB information centre, shop and café for the nature reserve in which it is situated, and affords a good view of South Stack and its lighthouse. In 2007, the tower was damaged by vandals who used it for a drunken party.

The South Stack Lighthouse is built on the summit of a small island off the north-west coast of Holy Island, Anglesey, Wales. It was built in 1809 to warn ships of the dangerous rocks below.

The South Stack Formation is a sequence of Cambro-Ordovician (Furongian to Tremadocian) metasedimentary rocks exposed in northwestern Anglesey, North Wales. The outcrop of this formation at South Stack was chosen as one of the top 100 geosites in the United Kingdom by the Geological Society of London, for its display of small-scale folding.

Gors is an area in the community of Trearddur, Ynys Môn, Wales, which is 140.8 miles (226.6 km) from Cardiff and 227.9 miles (366.8 km) from London.

The Holy Island Group is a sequence of metasedimentary rocks of Cambro-Ordovician (Furongian to Tremadocian) age found in northern and western Anglesey and the adjacent Holy Island in North Wales. It comprises four formations; a lower South Stack Formation, an overlying Holyhead Formation, a succeeding Rhoscolyn Formation and an uppermost New Harbour Formation. The South Stack Formation outcrops on Holy Island, between Holyhead and South Stack and at Rhoscolyn, and also inland on Anglesey itself between Mynydd Mechell and Carreglefn. The Holyhead and Rhoscolyn formations are restricted to the Holyhead Mountain and Rhoscolyn areas of Holy Island. The New Harbour Formation, which previously enjoyed 'Group' status, is some 2km thick and conformably overlies the Rhoscolyn Formation. It extends across much of northern and western Anglesey and Holy Island.