Holy Island ( Welsh : Ynys Gybi , ‘the island of (Saint) Cybi ‘) is an island (15.22 sq mi (39.4 km 2 )) on the western side of the larger Isle of Anglesey , Wales , from which it is separated by a narrow, winding channel. It is called “Holy” because of the high concentration of standing stones , burial chambers , and other religious sites on the small island. The alternative and historic name of the island is Holyhead Island . According to the 2011 Census , the population was 13,659, of which 11,431 (84%) lived in the largest town, Holyhead.
Irish pirates invaded Anglesey following the end of Roman rule in Britannia . Cunningham first defeat the Irish on the Irish but Cadwallon Lawhirdefeated the Irish on Holy Island.
There are a variety of natural habitats on Anglesey including mudflats , dunes, marshes , and beaches .  Neolithic farmers. Practically nothing is left of the oak forest .  The western side of the island is taken over by Holyhead Mountain , an area of maritime heather moor, which is the highest peak in the county at 722 feet (220 m). The coastal zone between the island and the mainland of Anglesey is a large site of special interest – Beddmanarch-Cymyran .
Holy Island is connected to Anglesey by two road links. The first, the Stanley Embankment , is made up of causeways carrying the A5 / A55 and the main railway line to Chester and London , and the original bridge of the A5 post road. The second is Four Mile Bridge , which carries a ‘B’ road and is much smaller.
The main settlement is the port of Holyhead , from which Laoghaire and Dublin , Ireland , and freight to Dublin. Holyhead railway station is located in the town. Other settlements include the villages of Trearddur Bay , Rhoscolyn , and Four Mile Bridge .
Around 30 miles (125 km) from the 125-mile (201 km) Anglesey Coastal Path is on Holy Island.
Peripheral islands and stacks include North Stack , and South Stack , with its famous lighthouse . Before – and even after – the construction of lighthouses, the cliffs and jagged rocks of the island were a great danger to sailors.
- Jump up^ Anglesey natural history
- Jump up^ Cambrian Archaeological Monographs No. 3. Trefignath and Din Dryfol. The excavations of two megalithic tombs in Anglesey. CA Smith and FM Lynch. Cambrian Archaeological Association 1986.ISBN 0 947846 01 8. ISSN 0266-593X