We took an all day tour to the Cliffs of Moher, about a 4 hour drive from Dublin. It was worth the trip. It's one of the most popular attractions in Ireland, regularly attracting over a million tourists per year. The cliffs have appeared in numerous movies including "Princess Bride" and " Harry Potter and the Half-Blood Prince" [*]
The cliffs reach their highest point of 702 feet above the sea, just north of O'Brien's Tower.
Being built near the highest point of the Cliffs of Moher, O'Brien's Tower offers the furthest views along the coast and of nearby islands. It was a bit hazy the day we were there, and a storm blew in shortly after we left the cliffs. But the view is almost always scenic despite the weather.
Although the well paved path from the visitor center to O'Brien's Tower is less than a half mile, it is a steady uphill walk. There's also a much longer, less improved trail you can hike along the cliffs. Of course being part of a fairly large tour group with a long drive back to Dublin, we didn't have that option. But if you're staying closer to the cliffs, such as Galway, and have an entire day you can walk more of the 18 km (11 mile) Cliffs of Moher Coastal Walk. Don't expect that hike to be on a well paved path though. Also, be sure to bring rain gear and be prepared for winds, the weather can and did change quickly from sunny to driving rain.
From a distance, the view of O'Brien's Tower and the Sea Stack (that pointy rock jutting from the water) is one of the most scenic.
Before heading back to Dublin our tour stopped at Galway for lunch. After lunch we walked around the town and visited some of the local stores. I, of course, had to buy a couple of the local beers for sampling later on.
Although Galway is a fairly small town with a population of less than 80,000 there are an amazing number of books which are set in Galway. As I'm writing this blog, Goodread lists 28 books that are set in Galway. My favorite is the Jack Taylor series, which I watched as a TV series before reading the books.