The Holyhead Breakwater is the longest in Britain and one of the great engineering achievements of the Victorian era. It encloses the New Harbour on the north side of Holy Island, providing a sheltered anchorage for the Irish Mail packets that once made Holyhead the most important port between London and Dublin. The lighthouse at the seaward end was completed in 1873.
Walking the full length — about an hour each way — is one of the better strolls in north Wales, exposed but spectacular, with the rugged coastline of the Gogarth cliffs to one side and the open Irish Sea on the other. Watch for grey seals in the harbour and the regular procession of Stena Line ferries arriving from Dublin and Dún Laoghaire.