South Stack is a tiny island off the western tip of Holy Island, reached by a steep flight of more than 400 steps and a small aluminium footbridge that replaced the cast-iron Victorian original in 1997. The white-painted lighthouse, completed in 1809 by Daniel Alexander, has guided shipping through the busy Irish Sea routes for two centuries. Inside, on guided tours, you can climb the spiral staircase to the lantern room and walk out onto the gallery for a giddy view of the cliffs.
The setting is as much of a draw as the building. The cliffs around the lighthouse are some of the best seabird breeding grounds in Wales — guillemots, razorbills, and puffins all nest here between April and July, and the RSPB operates a visitor centre at the top of the steps with telescopes trained on the cliff faces. The walk down and back up is steep enough to count as exercise.