My uncle lived in Kerry and gave me a tour of the neolithic circles and stone works. Required before you had to take him to the local pub for a few drinks. The whole area is full of things like this.
also the landscape (at least in cork) is dotted with ringforts, which were built from the bronze age through to 1000 ad. they consisted of earthen walls enclosing a small settlement with farm animals. my understanding is that almost none of them have been archaeologically excavated. nowadays they are usually considered unlucky and avoided by people.