There are a variety of natural habitats on the island 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 . Just off the coast by the mountain are located two islands North Stack and South Stack, upon the latter stands a lighthouse.