Brent L.
Yelp
Ross Castle is steep in Irish history and since it's in the middle of a national park, you can visit for free.
Or you can choose to book a trip with Killarney Tours. €32 per person gets you a ride in a "jaunting car" (a horse carriage) from the Killarney City Centre, and also a boat ride around Lough Leane. It's about a 40 minute carriage ride from the City Centre through the national park, and a little more than an hour cruise to tour the lough.
The carriage ride takes you from the city, and straight into the wooded areas of the beautiful national park. Very awesome views on this ride and the carriage driver had a lot of history about the castle, and interesting anecdotes to share.
After I arrived at the castle, I had time to explore for a bit before boarding the boat ride to tour the lough. The captain was also a wonderful tour guide and had plenty of stories about the history of the Ross Castle, as well as the history of the land around the lough. Plenty of gorgeous mountain scenery to take in on the boat tour. If you do only one thing, I highly recommend the boat tour. The scenery is spectacular.
Most of the outer walls of the castle still stand, but there's not a lot of interior areas to tour.
If you book through Killarney Tours, they will also shuttle you back to your hotel after the boat tour. BUT, they don't rush you. They allow you plenty of time to take a self guided tour of the Ross Castle before you leave.
Killarney Tours info can be found here: http://www.killarneylaketours.ie/choose-a-tour/combination-tour.html