Regarding O'Brien's Tower, internet sources give this description:
"O'Brien's tower was built in 1835 by Cornelius O'Brien, a descendant of Brian Boru, the High King of Ireland, and the O'Brien's of Bunratty Castle, Kings of Thomond, as an observation point for the hundreds of tourists who even then visited the Cliffs. O'Brien's Tower is the best location from which to view the Cliffs, from this vantage point one can see the Aran Islands, Galway Bay, as well as The Twelve Pins and the Maum Turk Mountains to the north in Connemara and Loop Head to the South."
"...the development of the first visitor centre at the location when Clare MP, Cornelius O'Brien, unwittingly started the country's fascination with visitor centres when he constructed O'Brien's Tower at the highest point of the world renowned Cliffs of Moher in 1835. Built as an observation point for "strangers visiting the magnificent scenery of this neighbourhood", the tower served tea and refreshments to visitors where they could take in the breathtaking views of the cliffs, the Aran Islands, the Kerry Mountains and the Twelve Bens in Connemara across Galway Bay."