Hook Lighthouse, Hook Head, Ireland

The banded tower on the bare limestone tip of Hook Head in County Wexford, guarding the entrance to Waterford Harbour. The squat lower stage is a medieval keep built in the early 13th century under the Norman lord William Marshal, which makes it one of the oldest lighthouses in the world still working; the exact year is uncertain, and local tradition places a monks' beacon here far earlier. Guided tours climb through the vaulted medieval rooms inside the walls.