O'Brien's Castle is a historic structure located on the Cliffs of Moher in County Clare, Ireland. Built in the 15th century, it was named after the O'Brien family, who were prominent rulers in the region. The castle offers stunning views of the Atlantic Ocean and the surrounding landscape, making it a popular tourist destination. The castle is a simple stone structure, featuring a square tower and thick walls. It was originally constructed for defensive purposes but has since become a symbol of Irish heritage. Visitors can explore the site and learn about its history, as well as enjoy the breathtaking scenery of the Cliffs of Moher.