From Wikipedia: O'Brien's Tower marks the highest point of the Cliffs of Moher in County Clare, Ireland, located a short distance from the village Doolin.
The tower was built on the cliffs in 1835 by local landlord Sir Cornellius O'Brien as an observation tower
for the hundreds of Victorian tourists that frequented the cliffs at the time.
Another version tells of O'Brien building the tower in order to impress women he was courting.

Either way, it's a delightful little tower. Costs a little to go up into it - we chose not to.