North Stack North Stack North Stack (Welsh: Ynys Arw, meaning "rugged island") is a small island situated just off Holy Island on the north-west coast of Anglesey. North Stack can also refer to the headland opposite the island. This is the site of a redundant fog warning station, comprising a number of buildings, including the Trinity House Magazine, built in 1861, where shells for the warning cannon were stored. These buildings now house a bird watching observatory, giving a view of South Stack lighthouse across Gogarth Bay, and the studio of artist Philippa Jacobs. The Precambrian quartzite cliffs of this headland, including
Holy Island, Anglesey Britannia. Cunedda first began warfare against the Irish but ultimately Cadwallon Lawhir defeated the Irish on Holy Island. There are a variety of natural habitats on Anglesey including mudflats, dunes, marshes, and beaches. Practically nothing is left of the oak forest that covered almost all of the island before the arrival of Neolithic farmers. The western side of the island is taken up mainly by Holyhead Mountain, an area of maritime heather moor, which is the highest peak in the county at . The coastal zone between the island and the mainland of Anglesey is a large site of special