Hook Head

This is the oldest operational lighthouse in the world, built by William Marshall (not single-handed - surely) in the early thirteenth century. It is the southernmost tip of the Hook Peninsula, which also features some dramatic ruins, such as St Dublin's Church and the rather odd Templetown , a settlement of the Knights Templar, from the 12th to the 14th century. 

Just north of there is the Irish version of Tintern Abbey, with some great views across low coastal marshes, and the wonderful Colclough Walled Gardens.