Some of the oldest rocks in Britain form the 125-mile coastline of the 85 square mile Anglesey Area of Outstanding Natural Beauty, which includes Holy Island with its busy port of Holyhead, the terminus for the Dublin ferry. The terrain inland is mainly a fertile plateau worn flat by the action of the sea, with low ridges and shallow valleys, while the sheer limestone cliffs of the east coast and on the north coast at Holyhead Mountain represent some of the most spectacular sea cliffs in Britain. 

On the steep northern and eastern cliffs, guillemots, choughs, cormorants and razorbills nest, while on the huge precipice of Gogarth Bay on lighthouse-topped South Stack (Ynys Lawd) on Holyhead Mountain, expert rock climbers now find their sport where local people formerly harvested gulls’ eggs from the vertiginous ledges.

Anglesey has a wealth of prehistoric remains. On the slopes of Holyhead Mountain, a collection of over 50 hut circles and rectangular enclosures, known as Cytiau’r Gwyddelod (Irishmen’s Huts), are thought to date from the Bronze Age and were still in use in Romano-British times, and many finds indicate the wealth of Iron Age culture on the island.