O'Brien's Tower is a round stone tower at the approximate midpoint of the cliffs. It was built by Sir Cornellius O'Brien, a descendant of Ireland's High King Brian Boru, in 1835, as an observation tower for the hundreds of tourists that frequented the cliffs even at that date. From atop that watchtower, one can view the Aran Islands and Galway Bay, the Maum Turk Mountains and the Twelve Pins to the north in Connemara, and Loop Head to the south.